Dept of MS&E
Case Western Univ
Cleveland, OH 44106-7204
Dept Chem Eng & Matls Sci
Univ of Minnesota
151 Amundson Hall
Minneapolis, MN 55455
Dept of Ceramic & Materials Engr
Piscataway, NJ 08854-8065
Univ of Cincinnati
Cincinnati, OH 45221-0172
*3M Advanced Materials Technology Center
Proceedings published as Volume 576
*Chemat Technology, Inc.
*Dow Chemical Company
*Eastman Kodak Company
of the Materials Research Society
Symposium Proceedings Series.
* Invited paper
SESSION DD1: SYNTHESIS AND PROCESSING I
8:30 AM *DD1.1
ORGANIC/INORGANIC MOLECULAR HYBRID MATERIALS FROM CUBIC
SILSESQUIOXANES. R.M. Laine , C. Zhang, M.C. Gravel, A. Sellinger, N.L.
Dias Filho, H. Nyguen, L. Viculis and Q. Zhu, Departments of Materials
Science and Engineering, Chemistry, and the Macromolecular Science and
Engineering Center, University of Michigan, Ann Arbor, MI.
Chair: Florence Babonneau
Monday Morning, April 5, 1999
Salon 11/12 (M)
Octafunctionalized silsesquioxanes [(RSiO1.5),
cubes] offer potential as rigid, hard nanoplatforms to which a variety
of organofunctional groups can be appended. In principle it is possible
to create octafunctional macromonomers that at the synthetic level are
useful as cross-linking agents, building blocks for novel polymeric materials,
initiation sites for dendrimer syntheses, etc. In the materials arena,
functionalized cubes offer access to nonporous materials, nanoreinforced
composites or materials that act as hosts for other molecules, etc. We
describe here the synthesis and characterization of several new functionalized
cubes and several novel, materials with useful mechanical properties and
high temperature stability.
9:00 AM DD1.2
DISCRETE POLYEDRAL Si/O FRAMEWORKS AS PRECURSORS TO HYBRID
ORGANIC-INORGANIC THERMOPLASTICS. Frank J. Feher , Frank Nguyen, Daravong
Soulivong, Richard Brutchey, Dept of Chemistry, University of California,
Irvine, CA; Joseph D. Lichtenhan, Joseph J. Schwab, Hybrid Plastics, Fountain
Fully condensed polyhedral oligosilsesquioxanes (i.e.,
[RSiO3/2]n) and spherosilicates (i.e., [(R3SiO)SiO3/2]n)
are attractive feedstocks for the manufacture of polymerizable Si/O frameworks.
This talk will describe several practical methods for producing structurally
well-defined Si/O monomers from readily available polyhedral silsesquioxanes
and spherosilicates, including R6Si6O9
and R8Si8O12 frameworks.
9:15 AM DD1.3
NANOCOMPOSITES OF SILOXANE AND SILSESQUIOXANES WITH DIELS-ALDER
POLYMERS. Raef M. Shaltout , Douglas A. Loy, Encapsulation and Foams Department,
Sandia National Laboratories, Albuquerque, NM.
In-situ filling through hydrolysis and condensation of
silicon alkoxides has been utilized to generate nanocomposites in which
the filler phase can be intimately associated with the polymer on relatively
small length scales. One problem of the method has been achieving useful
fill volumes without bulk phase separation of the reacting silicon monomer
from the polymer. In this paper, we describe the preparation of a new class
of nanocomposite materials in which the filler phase is pre-assembled before
formation of an organic, Diels-Alder polymer. Maleimide monomers, prepared
from alkoxysilylpropyl amines and maleic anhydride, were protected against
side reactions by forming the oxonorbornene Diels-Alder adduct with furan.
The monomers were then reacted under sol-gel conditions to form oligomers
or polymers-the filler phase. These materials were then heated in the presence
of a co-monomer containing two or more furyl groups, thereby exchanging
the more volatile furan protecting group for the furyl co-monomer and creating
a composite material. Details of the preparation and characterization of
the materials will be given.
9:30 AM DD1.4
CHARACTERIZATION OF ORGANICALLY MODIFIED SILICATES BY
17O SOLID STATE MAS AND MQ-MAS NMR. Virginie Gualandris, Florence
Babonneau , Chimie de la Matiëre Condensée, UPMC-CNRS, Paris,
FRANCE; Pierre Florian, Dominique Massiot, CNRS-CRMHT, Orléans,
Hydrolysis and condensation of various organosilanes (RSi(OR')4-x,
R'=Me, Et, x=0,1,2) lead to the formation of hybrid networks in which organic
R groups are directly grafted on the silicate network. The spatial distribution
of the various Si units in the final gel network depends on the chemical
reactivity of the starting monomeric precursors, and will strongly influence
the properties of the final materials (mechanical strength, hydrophobicity...).
It is thus important to find characterization tools to probe the spatial
arrangment of the various sites and this paper will highlight the use of
17O solid state NMR. Organically modified silicates have been
prepared, using methyltriethoxysilane and tetraethoxysilane in various
ratios. The final network is thus composed of trifunctionnal T units and
tetrafunctionnal Q units. Three types of oxo bridges can be formed through
the competitive self-condensation or co-condensation reactions : (T)-O-(T),
(Q)-O-(Q) and (T)-O-(Q). 17O-enriched water was used as reactant
in order to selectively enrich the various oxo bridges, and to perform
17O solid state MAS-NMR. The combination of MAS NMR experiments
recorded at two different magnetic fields, and of the recently discovered
MQ-MAS experiments allowed us to identify clearly the three types of oxo
bridges. Quantitative analysis was then extracted from the MAS-NMR spectra,
and compared with calculations based on randomly distibuted Si units.
9:45 AM DD1.5
STORAGE STABILITY OF SOLVENT-FREE CONDENSATES OF FUNCTIONALIZED
TRIALKOXYSILANES. Sabine Stein , Stefanie Cramer von Clausbruch, Norbert
Moszner, Volker Rheinberger, IVOCLAR AG, Schaan, Principality of Liechtenstein.
The lack of storage stability of organic-inorganic solvent-free
sols is a well-known problem. We investigated the influence of different
solvents in the acid catalyzed hydrolysis of various sols on their storage
stability. Our experiments were founded on two different silanes, 3-methacryloxypropyltrimethoxysilane
(MPTS) and 1,1,1-tris(allyloxymethyl)-1-[[[3-(triethoxysilyl)propyl]amino-
carbonyl]oxymethyl]methane (Si 31), synthesized by reaction of pentaerythritol
triallyl ether and 3-isocyanatopropyltriethoxysilane. The employed solvents
were alcohol, tetrahydrofurane and tert.-butyl methyl ether in a range
of 30 to 95
in solution. In order to get comparable chemical conditions the degree
of condensation of the various sols were adjusted between 75
and 80. Furthermore, the sols were modified
by silylation with trimethylchlorosilane. A comparison of the silylated
and nonsilylated silanes clearly showed that a decrease in residual silanol
groups increase the storage stability. The results of the investigations
demonstrated that the storage stability of solvent-free condensates of
functionalized trialkoxysilanes depends significantly on the kind and also
on the amount of solvent used in hydrolysis.
10:00 AM DD1.6
NEW ORGANIC-INORGANIC POLYMERS USEFUL AS TARGETS IN INERTIAL-CONFINEMENT
FUSION EXPERIMENTS. Franck David Quillot, Didier Marsacq , CEA-DAM, Monts,
FRANCE; Alain DuchEne, Faculte des Sciences, Laboratoire PIMIR, Tours,
FRANCE; Jean Marie Catala, Institut Charles Sadron, Strasbourg, FRANCE.
Original organic-inorganic polymers and copolymers useful
as targets in inertial-confinement fusion experiments are under development.
Such polymers can be employed to prepare fuel container or targets as form
as microballon or polymer foams. The presence of metal atoms such as silicon
or germanium is required during experiments to convert laser energy in
X-ray energy. The atomic composition of polymers is a relevant parameter.
They must be exclusively composed with hydrogen and metal atoms without
oxygen or other impurities. Homopolymers and copolymers of styrene and
p-functionnalized styrene are prepared by using nitroxide-mediated living
free radical polymerization. This polymerization technic allows us to produce
microballons exhibiting high sphericity and wall uniformity because of
the low molecular weight dispersion. The synthesis and reactivity of p-functionnalized
styrene bearing an organometallic function are examined. The physical properties
of corresponding polymers are also described.
10:45 AM *DD1.7
SOL-GEL POLYMERIZATION OF ORGANOTRIALKOXYSILANES EFFECT
OF THE ORGANIC SUBSTITUENT ON GELATION. Douglas A. Loy , Brigitta M. Baugher,
Duane A. Schneider, Encapsulation and Foams Department, Sandia National
Laboratories, Albuquerque, NM.
are a family of siloxane network polymers that have become important as
vehicles for introducing organic functionalities into sol-gel materials.
However, there has not been a systematic study of the ability of organotrialkoxysilanes
to form gels through the sol-gel process. In this study, we have examined
the sol-gel chemistry of a variety of organotrialkoxysilanes (RSi(OR')3)
with different organic groups (R = H, Me, Et, Pr, i-Pr, n-Bu, i-Bu, t-Bu,
hexyl, octyl, decyl, dodecyl, hexadecyl, ocatdecyl, cyclohexyl, vinyl,
phenyl, benzyl, phenethyl, chloromethyl, cyanoethyl, chloromethylphenyl,
aminopropyl) with methoxide or ethoxide substitutents on silicon, at varying
monomer concentrations, and with acidic and basic catalysts. In general,
three different groups of materials were obtained. Many of the monomers
reacted to form crystalline oligomers or polyhedral oligosilsesquioxanes.
The majority of the polymerization experiments produced resinous oligomers
or polymers. A minority of the polymerization experiments afforded gels.
Gels obtained from these polymerizations were processed as xerogels and
characterized by solid state NMR, microscopy, and nitrogen sorption porosimetry.
11:15 AM DD1.8
PREPARATION AND PROPERTIES OF INORGANIC-ORGANIC HYBRIDS
FROM VINYL- AND 3-METHACRYL- OXYPROPYLTRIMETHOXYSILANE. Norihiro Takamura
, Takahiro Gunji, Yoshimoto ABE Department of Industrial Chemistry, Faculty
of Science and Technology, Science University of Tokyo, Yamazaki, Noda,
Inorganic-organic hybrids have been focused on as a candidate
to create a novel material composed of organic and inorganic structures
bonded through covalent linkages. Tailoring the hybrids, therefore, are
expected to provide multifunctional coating materials with properties such
as high transparency, thermal stability, and scratch resistance as well
as insulators and dielectrics. The synthetic routes would be sol-gel process
or precursor method using silanes or metal organic compounds. Vinyl- and
3- methacryloxypropyltrimethoxysilane (VTS and MAS) are preferable starting
materials to prepare polyvinylpolysilsesquioxane (PVPS) and poly-3- methacryloxy-
propylpolysilsesquioxane (PMPS), respectively. These can be precursors
to not only coating films but also hybrid films to investigate the relationship
between the structure and properties of precursor polymers and materials.
PVPS and PMPS were prepared by radical polymerization of VTS and MAS, respectively,
with t-butyl peroxide at 150C
for 2 h followed by acid- catalyzed hydrolysis. Those were transparent
and viscous solutions and gave gel films by casting the 20 wt% acetone-
methanol solutions of PVPS and PMPS on the polymethylpentene shale at 80C
for several days. The gel films thus prepared were highly transparent and
flexible. The thickness of PMPS gel films was 0.02 mm. The tensile strength
of films was dependent on the degree of polymerization of organic group
which was estimated by GPC analysis. When the degree of polymerization
of organic group is increased from 10 to 48, the tensile strength is decreased
from 9.7 to 3.6 MPa but the film was more flexible. This is the reason
why the formation of siloxane bonds was prevented by steri
11:30 AM DD1.9
EFFECT OF METAL ALKOXIDE ADDITION ON HYDROLYSIS AND CONDENSATION
REACTIONS OF PHENYLTRIETH- OXYSILANE. Ikuko Yoshinaga , Noriko Yamada,
Shingo Katayama, Nippon Steel Corporation, Advanced Technology Research
Laboratories, Kawasaki, JAPAN.
Inorganic-organic hybrids containing phenyl groups as
an organic component are expected to provide peculiar properties because
of the thermal stability and steric effect of phenyl groups. We have incorporated
various inorganic components into a phenylsiloxane network derived from
phenyltriethoxysilane (PTES) in order to alter the properties of the hybrids
in a wide range. Metal alkoxides as an inorganic precursor were found not
only to alter the properties, but also to accelerate the condensation reaction
of PTES. The 29Si-NMR study revealed that the chemical shifts
for T3 were developed by the addition of metal alkoxides into
the reaction system of PTES. The acceleration effect was also found to
depend on metal alkoxides. Ti ethoxide and Al buthoxide significantly accelerated
the condensation reaction as compared with Ta ethoxide. The difference
in acceleration of the condensation reaction of PTES is thought to result
from the reactivity of metal alkoxides toward hydrolyzed PTES.
Research supported by NEDO, under the Synergy Ceramics
Project of the ISTF program promoted by AIST, MITI, Japan.
11:45 AM DD1.10 X-RAY AND NEUTRON SMALL ANGLE SCATTERING
INVESTIGATION ON PRECURSOR DERIVED B-C-N CERAMICS. Dieter Heinrich Sauter
, Joachim Bill, Universitat Stuttgart, Insitut für Nichtmetallische
Anorganische Materialien, Stuttgart, GERMANY; Peter Lamparter, Stefan Schempp,
Max-Planck-Insitut für Metallforschung, Stuttgart, GERMANY; Fritz
Aldinger, Universitat Stuttgart, Insitut für Nichtmetallische Anorganische
Materialien and Max-Planck-Insitut für Metallforschung, Pulvermatallurgisches
Laboratorium, Stuttgart, GERMANY.
The synthesis of elementoorganic polymers and their subsequent
transformation into inorganic materials by thermolysis is a novel approach
to design new materials providing semiconducting properties and high oxidation
resistance at high temperatures. Amorphous B28C40N32
ceramics were produced by thermolysis of a polyborcarbodiimide precursor
at 1100C in argon gas atmosphere.
X-ray wide angle scattering shows that the samples are fully amorphous
up to 1600C. In order to investigate
the medium range structure of the amorphous ceramics, small angle scattering
experiments were performed. For the identification of the scattering centres
the methode of contrast variation was employed. This was achieved by combination
of small angle X-ray scattering (SAXS) experiments with small angle neutron
scattering (SANS) measurements. In order to suppress the influence of surface
scattering the immersion technique with suitable mixtures of C2H5OH
and C2D5OD was applied. These experiments revealed,
that the amorphous ceramics contain heterogeneities in the order of 20
caused by phase separation in the amorphous matrix. Further on, the temperature
dependence of the medium range structure of the samples was investigated.
A strong temperature-time dependence is determined considering the Guinier
radius of the scattering regions of the annealed samples. Investigations
of the crystallisation process during heat treatment up to 2000C
suggest the formation of a carbon rich ternary boroncarbonitride phase.
SESSION DD2: SYNTHESIS AND PROCESSING II
1:30 PM DD2.1
ORGANIC-INORGANIC HYBRID MATERIALS FROM SURFACE INITIATED
POLYMERIZATION. Thomas A.P. Seery and Fatma Vatansever University of Connecticut,
Chemistry Department and Polymer Program, Storrs, CT.
Chair: Douglas A. Loy
Monday Afternoon, April 5, 1999
Salon 11/12 (M)
Organic-inorganic hybrids must overcome the thermodynamic
tendency to phase separate. This is an especially urgent issue during processing
when it is desirable to disperse nanoscale particles of one component (inorganic)
phase throughout a second (organic) phase. Control of the interface between
phases becomes a critical issue for the preparation of high performance
materials. Silane coupling agents are one means to prepare a silica surface
and we have extended this approach by polymerizing from the distal end
of such a coupling agent. End functional coupling agents have been used
to attach ruthenium alkylidene catalysts for ring opening metathesis polymerization
of cyclooctadiene and norbornenes. Polymerization of cyclooctadiene monomers
yield 1,4 butadiene chains on silica surfaces that are candidates for dielectric
strength enhancers in high voltage applications. Thermogravimetric analysis
is used to obtain the ratio of organic to silicate. Thermal desorption
GC-MS provides a means of probing surface-bound species. The nanometer
dimensions of the silica make it dispersible in solution so that standard
methods of synthetic organic chemistry e.g. NMR, IR - may be used
to analyze the intermediates. NMR has been particularly useful in observing
the shift of the alkylidene proton (18-21 ppm in a proton spectrum) as
an indicator of whether the catalyst is bound to the surface or not.
1:45 PM DD2.2
SYNTHESIS AND CHARACTERIZATION OF HYBRID ORGANIC-INORGANIC
NANOPARTICLES USING CONTROLLED/LIVING RADICAL POLYMERIZATIONS. Timothy
von Werne, Timothy E. Patten , Univ of California at Davis, Dept of Chemistry,
Recently developed controlled / living radical polymerizations
provide the means to prepare a wide range of polymers with narrow molecular
weight distributions and accurate control over their final molecular weights.
Nanoparticles, depending upon their composition, exhibit novel magnetic,
optical, and materials properties that can be ascribed to their small size
and large surface areas. The incorporation of nanoclusters into polymeric
materials and the ordering of nanoclusters into superlattices or extended
periodic arrangements are important steps in exploiting the properties
of these unusual materials. Recently, several approaches to preparing well-defined
nanocluster-based structures have been reported. These methods involve
the use of DNA conjugates, self-organization, and monolayer formation to
define the spatial orientation of the nanoclusters. A polymer-based approach
to organizing nanoclusters would combine the spatial definition afforded
by the aforementioned techniques with the versatile film-forming and mechanical
properties of polymers. We have developed a method to prepare novel, well-defined
organic-inorganic nanoparticles by integrating the techniques of colloid
and nanocluster synthesis with those of newly developed living radical
polymerizations. We have synthesized initiators for atom transfer radical
polymerization (ATRP) that possess alkoxysilane functional groups. A monolayer
of these bifunctional initiators were attached to 60
nm spherical silica particles to yield macroinitiators for ATRP. The attachment
of the initiator was confirmed using elemental analysis, TGA, and diffuse
reflectance infrared Fourier transform (DRIFT) spectroscopy. Particle diameters
and the unaggregated state of the particles were confirmed in films using
SEM and TEM and in solution using dynamic light scattering (DLS). These
macroinitiators were used in styrene ATRP to yield nanoparticles with a
silica core and polystyrene outer layer. Growth of the polymer from the
surface of the nanoparticle was confirmed using kinetics and DLS measurements.
These hybrid nanoparticles were cast from organic solvents to yield composite
2:00 PM *DD2.3
DIFFERENT SOLVENT FREE SYNTHETIC ROUTES TO ORGANIC/INORGANIC
HYBRID MATERIALS. Jean-Pierre Pascault , Hamid Kaddami, Jean-Franáois
Gérard, Institut National des Sciences Appliquées de Lyon,
Laboratoire des Matériaux Macromol, Villeurbanne, FRANCE.
The sol-gel chemistry in low-temperature conditions can
be used to produce organic-inorganic (O/I) materials nanocomposite from
i.e. the in-situ formation of silica-rich phase in a polymer matrix. Different
solvent free synthetic routes have been proposed : i) hydrolysis and condensation
reactions of silane end capped oligomers prepared by one or two stages.
The disadvantage of this route is that the concentration of inorganic clusters
is generally low, i.e. 2-3 % bw ii) simultaneous hydrolysis / condensation
of tetraethoxysilane and polymerization of an organic monomer. The choice
of an alcoholic monomer as hydroxyethyl(meth)acrylate, HE(M)A allows to
work without any addition of solvent. In this case morphologies having
bicontinuous structure can be obtained. iii) polymerization of an organic
monomer in presence of preformed functionalized silica nanoparticles (
10nm in diameter). Similar concentrations of inorganic phase but quite
different morphologies than case ii) can be prepared in this case. Rheological
investigations made during the polymerization of these different systems,
display many differences, depending on the synthesis route and the silica
content. The morphologies and the phase compositions were studied by means
of different techniques. These parameters can be controlled both from the
method of synthesis and by changing the acid catalyst concentration of
the sol gel chemistry. iv) More recently a quite different synthesis method
has been proposed : functionalized polyhedral silsesquioxanes(R Si O1.5)n
are first synthesized and then copolymerized with organic monomers or precursors
as polyurethane ones.
2:30 PM DD2.4
SOL-GEL CHEMISTRY BY RING OPENING POLYMERIZATION. Douglas
A. Loy, Kamyar Rahimian , Encapsulants and Foams Department, Sandia National
Laboratories, Albuquerque, NM.
Sol-gel processing of materials is plagued by shrinkage
during polymerization of the alkoxide monomers and processing (aging and
drying) of the resulting gels. We have developed a new class of hybrid
organic-inorganic materials based on the solventless ring-opening polymerization
(ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl
group, which permits us to drastically reduce shrinkage in sol-gel processed
materials. Because the monomers are polymerized through chain growth mechanism
catalyzed by base rather than the step growth mechanism normally used in
sol-gel systems, hydrolysis and condensation products are entirely eliminated.
Furthermore, since water is not required for hydrolysis, an alcohol solvent
is not necessary. Monomers with two disilaoxacyclopentyl groups, separated
by a rigid phenylene group or a more flexible alkylene group, were prepared
through disilylation of the corresponding diacetylenes, followed by ring
closure and hydrogenation. Anionic polymerization of these materials, either
neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer,
affords thermally stable transparent gels with no visible shrinkage. These
materials provide an easy route to the introduction of sol-gel type materials
in encapsulation of microelectronics, which we have successfully demonstrated.
2:45 PM DD2.5
DENDRIMER-METAL NANOCOMPOSITES. Lajos Balogh , University
of Michigan Center For Biologic Nanotechnology, Ann Arbor, MI; Donald A.
Tomalia, Michigan Molecular Institute, Midland, MI; Kenneth S. Laverdure
and Samuel P. Gido, University of Massachusetts Amherst, Polymer Science
and Engineering, Amherst, MA; Andrew G. Mott, Mary J. Miller and Brian
P. Ketchel, AMSRL-SE-EO, Gaithersburg, MD.
Dendrimer metal nanocomposites are novel hybride materials
that display unique physical and chemical properties as a consequence of
the atomic/molecular level dispersion of an inorganic guest within a dendrimer
host. In their synthesis, dendrimers are used as templates to pre-organize
metal ions followed by an in-situ reduction, which will immobilize and
stabilize atomic domains of the reaction product(s). Size, shape, size
distribution and surface functionality of these nanocomposites are determined
and controlled by the dendritic macromolecules and may also be influenced
by the encapsulated compounds. In this work, surface-modified poly(amido-amine)
dendrimers were used to prepare Cu(0)-PAMAM, Ag(0)-PAMAM and Au(0)-PAMAM
dendrimer-metal nanocomposites containing stable and solvent soluble zero
valent metals. Characterization of the resulting nanocomposites has been
carried out by TEM, UV-visible spectroscopy, scattering techniques, etc.
The role of ion preorganization in the resulting nanocomposite structures
as well as their chemical and optical properties will be compared and discussed
including potential applications.
3:30 PM DD2.6
POLYMER CRYSTALLIZATION STUDIED IN CONFINED DIMENSIONS.
Frank-Dieter Kuchta , Piet J. Lemstra, Dutch Polymer Institute (DPI), Eindhoven,
THE NETHERLANDS; Hartmut R. Fischer, TNO-TPD Materials Research & Technology,
Eindhoven, THE NETHERLANDS.
The aim of the present study is to link the fundamental
research field of polymer crystallization with the technical important
field of the preparation and the properties of polymer-layered silicate
nanocomposites. It is known that semi-crystalline polymers crystallize
in different phases (e. g. monoclinic, hexagonal) forming chain-folded
lamellar. Depending on experimental conditions (e. g. temperature, pressure)
the crystal size (lamellar thickness) is affecting the stability of these
phases. The incorporation of layered silicates acting as hard walls into
semi-crystalline polymers opens now new possibilities: i) To study polymer
crystallization in confined dimensions; ii) To provide materials from commodity
or engineering polymers with new or enhanced properties. From the fundamental
work of researchers at Toyota Central Research and Development Laboratories
on nanocomposites based on polyamide-6 and layered silicates it became
apparent, that polyamide-6 does not crystallize in the monoclinic but in
the hexagonal form. This form exhibits advantageous properties (e. g. higher
toughness, barrier properties) hence it is of technical interest. Within
the present investigation the effect of an external confinement introduced
by highly anisotropic silicate layers of organically modified clay minerals
on crystal growth and nanocomposite properties has been studied on polyamide-6,
polyamide-11, polyethylene and polypropylene. The composites were prepared
both by in situ polycondensation and by reactive blending via melt extrusion.
All nanocomposites exhibit a homogeneous distribution of individual silicate
layers within the host polymer at low clay content. The lamellar thickening
growth is reduced in polyamide crystallization due to the external constrained
of the silicate layers in the host polymer. In polyamide-11 crystallization
a phase transition (triclinic/hexagonal) is expected at higher clay contents.
Furthermore the nanocomposite shows an enhanced thermal stability and tensile
3:45 PM DD2.7
MELT INTERCALATION OF PMMA INTO LAYERED SILICATES. Zhiqi
Shen , George P. Simon, Yi-Bing Cheng, Monash Univ., Dept. of Materials
Engineering, Clayton, Melbourne, AUSTRALIA.
Organic-inorganic hybrid materials have recently attracted
much interest, especially polymer-silicate hybrids. PEO, PS and a series
of styrene-dervative polymers were reported to intercalated into layered
silicates via melt intercalation. In this study, intercalation of PMMA
with various tacticities and molecular weights is attempted via a melt
intercalation process. The organic-inorganic nanocomposites are characterized
by XRD, DSC, TGA and FTIR. Saturation ratio of polymer to silicate is deduced
from severval techniques and the effect of processing and resultent thermal
properties of PMMA-silicate hybrids are studied.
4:00 PM DD2.8
MODELING THE INTERACTIONS BETWEEN POLYMERS AND CLAY SURFACES
THROUGH SELF-CONSISTENT FIELD THEORY. Anna C. Balazs , Chandralekha Singh
and Ekaterina Zhulina, Department of Chemical and Petroleum Engineering,
University of Pittsburgh, Pittsburgh, PA.
Using numerical self-consistent field (SCF) calculations,
we investigate the interactions between two closely-spaced surfaces and
the surrounding polymer melt. Short chains (surfactants) are terminally
anchored to each of the surfaces. The coated substrates model orginally-modified
clay crystallites (sheets). Through the calculations, we vary the characteristics
of the surfactants and polymers to isolate conditions that drive the polymer
to penetrate the gap between the surfaces. We also consider the effect
of employing end-functionalized chains to promote the dispersion of bare
clay sheets within the polymer matrix. We find that this scheme provides
a robust method for exfoliating the sheets. To consider this case in greater
depth, we develop an analytical SCF theory to model the interactions among
the functionalized chains, nonfunctionalized polymers and the clay sheets.
The results from the numerical and analytical SCF models show good agreement
on the behavior of the system. The results indicate that the optimal polymeric
candidates for creating stable exfoliated composites are those that would
constitute optimal steric stabilizers for colloidal suspensions.
4:15 PM *DD2.9
NANO AND MICROSCALE PATTERNING OF ORGANIC/INORGANIC FUNCTIONAL
COMPOSITES. Ilhan A. Aksay , Princeton University, Department of Chemical
Engineering and Princeton Materials Institute, Princeton, NJ.
This presentation will focus on the synthesis and processing
of organic/inorganic composites on two distinct length scales: (i) Self-assembly
of organic surfactants is used to generate patterns at the 10
to 1 micron length scale; and (ii) field-assisted alignment is used to
generate patterns at length scales larger than 1 micron. The utilization
of such nanostructured building blocks for the construction of larger,
viable composite materials can be accomplished through lamination of thin
films and patterning through microcontact printing and electrohydrodynamic
(EHD) manipulation of fluids. Extension of these patterning methods to
ceramics such as BaTiO3 and PbOZrO2TiO2
(PZT) are of interest for several reasons. First, their high dielectric
constants allow them to achieve high capacitances even with thick layers
and/or small area. This allows one to overcome a major limitation of some
printed insulator work today, where pinhole limitations are a major problem
for achieving high capacitances, e.g. in the F
range as might be required for de-spiking capacitors in real circuits.
Second, ferroelectrics such as BaTiO3 can be used in non-volatile
memory structures and have advantages over conventional MOS types of non-volative
memory in many applications. We have patterned dielectric or piezoelectric
films (BaTiO3, PbOZrO2TiO2
(PZT), and Pb(Zn1/3Nb2/3)O3 (PZN) on substrates such as silicon
and steel at temperatures below 650C.
Electron microscopic characterization of the patterned PZT thin films shows
that they can be converted to a single crystalline form where the dimensions
of the single crystal are defined by the width and the height of the pattern
SESSION DD3: NOVEL ORDERED HYBRID STRUCTURES
8:30 AM *DD3.1
EVAPORATION-INDUCED SELF-ASSEMBLY OF ORDERED NANOPOROUS
AND NANOCOMPOSITE FILMS AND POWDERS. C.J. Brinker , A. Sellinger, Y. Lu,
H. Fan, N. Huesing, D. Doshi, N. Doke, G. Lopez and T. Ward, The University
of New Mexico, Sandia National Laboratories Advanced Materials Lab, Albuquerque,
Chair: Timothy E. Patten
Tuesday Morning, April 6, 1999
Salon 11/12 (M)
Beginning with a dilute, homogeneous solution of ethanol,
water, surfactant, and soluble silica, we previously demonstrated the rapid,
continuous formation of ordered mesostructured films by dip-coating. Preferential
evaporation of ethanol enriches the depositing film in surfactant, water
and silica inducing, micellization and further self-organization into a
variety of ordered silica-surfactant mesophases (hexagonal, cubic, lamellar).
This presentation will provide a brief overview of our evaporation-induced
self-assembly approach followed by a discussion of recent work where we
extend this approach to prepare hybrid, organic-functionalized silica frameworks
as well as metal-silica and (organic) polymer-silica nanocomposites. In
the latter example we exploit the amphiphilic nature of surfactant molecules
or block copolymers to simultaneously organize inorganic and organic precursors
into highly-ordered nanocomposite films and particles in a rapid, evaporation-induced
self-assembly process. Finally I will discuss recent work where we combine
our self-assembly approach with micro-contact printing or optical lithography
to produce patterned mesostructured surfaces. Sandia is a multiprogram
laboratory operated by Sandia Corporation, a Lockheed Martin Company, for
the United States Department of Energy under Contract DE-AC04-94AL85000.
9:00 AM DD3.2
AEROSOL-ASSISTED SELF-ASSEMBLY OF SPHERICAL, SILICA NANOPARTICLES
EXHIBITING HEXAGONAL, CUBIC, AND VESICULAR MESOPHASES. Yunfeng Lu , Hongyou
Fan, Aaron Stump, Timothy L. Ward, Thomas Reiker and C. Jeffrey Brinker,
University of New Mexico, NSF Center for Micro-Engineered Materials, The
Advanced Materials Laboratory, Sandia National Laboratories.
Nanostructured particles exhibiting well-defined pore
sizes and pore connectivities (1-, 2, or 3-dimensional) are of interest
for catalysis, chromatography, controlled release, and custom-designed
fillers, pigments and optical hosts. During the last several years considerable
progress has been made on controlling the macroscopic forms of mesoporous
silicas prepared by surfactant and block copolymer liquid crystalline templating
procedures. Typically interfacial phenomena are used to control the macroscopic
form (particles, fibers, or films), while self-assembly of amphiphilic
surfactants or polymers is used to control the mesostructure. To date,
although a variety of spherical or nearly-spherical particles have been
prepared, their extent of order is limited as is the range of attainable
mesostructures. We report a rapid, aerosol process that results in solid,
completely ordered spherical particles with stable hexagonal, cubic, or
vesicular mesostructures. Our process relies on evaporation-induced interfacial
self-assembly (EISA) confined to a spherical aerosol droplet. The process
is simple and generalizable to a variety of materials combinations. Additionally,
it can be modified to provide the first aerosol route to the formation
of ordered mesostructured films.
9:15 AM DD3.3
SELF-ASSEMBLY OF MESO-SCALE AND NANO-SCALE PARTICLES
AND ITS APPLICATIONS. Younan Xia , Byron Gates, Sang Hyun Park, University
of Washington, Department of Chemistry, Seattle, WA.
We have demonstrated a simple and practical method for
the assembly of meso- and nano-scale particles into 3-D ordered lattices
over relatively large areas. The particles that we have used include silica
colloids and polymer latexes with diameters in the range of 50 nm to 50
um. This method provides an effective route to inorganic-organic composite
materials with highly ordered 3-D structures. We have used this method
to fabricate functional hybrid materials that can be used as tunable optical
filters, photonic band gap structures, and 3-D porous membranes.
9:30 AM DD3.4
MONODISPERSE MICRON SCALE TITANIUM DIOXIDE SHELLS ENCAPSULATING
POLYSTYRENE SPHERES. Vinothan N. Manoharan , Pingyun Feng, Department of
Chemical Engineering, University of California, Santa Barbara, CA; David
J. Pine, Departments of Chemical Engineering and Materials, University
of California, Santa Barbara, CA.
We present a method of producing monodisperse spherical
titanium dioxide shells with diameters on the order of one micron. First
monodisperse polystyrene spheres are synthesized by either emulsion or
dispersion polymerization. The spheres are then swollen in a uniform and
controlled manner by a mixture of organic solvent and titanium alkoxide
emulsified in a nonaqueous polar solvent (formamide), so as to prevent
hydrolysis of the alkoxide. When water is added to the resulting monodisperse
emulsion, the alkoxide gels at the interface between the droplet and the
continuous phase, producing a titanium dioxide shell; at the same time
the alcohol liberated by gelation changes the solvent quality in the droplet,
causing the original polystyrene sphere to precipitate inside the shell.
The product, titania shells encapsulating polystyrene spheres, is a strongly
scattering monodisperse colloidal suspension. It may be of interest in
the production of materials such as photonic crystals operating at optical
wavelengths. Because of the relatively low concentration of titanium needed,
it may be also of use in the manufacture of coatings and paints. We have
applied a similar method to the production of silicon dioxide shells.
9:45 AM DD3.5
FORMATION OF MESOSCOPIC POLYMER DOTS ON SILICON BY RUBBING
TRANSFER. Masahito Sano , Junko Okamura, Seiji Shinkai, Chemotransfiguration
Project - JST, Kurume, Fukuoka, JAPAN.
Regular arrays of poly(ethylene) deposits, about 10 nm
high and 160 nm in diameter, separated by 340 nm, are formed by simply
rubbing the polymer plate against the flat surface of silicon. In general,
the polymer transfer can be categorized into four situations: no transfer,
macroscopic depositions, nanometer-scale depositions with or without oriented
dots. There exist ranges of the conditions that the mesoscopic dot formation
occur. The substrate temperature must be below and close to the bulk melting
point of the polymer. At a given temperature, the rubbing rate must be
within a certain range to induce mass transfer. The silicon surface needs
to be prepared so that the polymer wets completely. While high and low
density polymers showed the analogous results, a low-molecular weight,
linear polymer failed to produce mesoscopic dots. This means that viscoelastic
properties and wetting characteristics, rather than surface tensions, are
important in dot formation.
SESSION DD4: STRUCTURE & PROPERTIES OF ORGANIC
10:30 AM *DD4.1
SYNTHESIS OF STRUCTURED ORGANIC/III-V SEMICONDUCTOR INTERFACES
VIA SELF-ASSEMBLY WITH CHALCOGENIDE-FUNCTIONALIZED MOLECULES. D.L. Allara
, C.A. Mars, Pennsylvania State University, Dept. of Chemistry, University
Park, PA; J.M. Tour and W.E. Reinerth, University of South Carolina, Dept.
of Chemistry and Biochemistry, Columbia, SC.
Chair: Timothy E. Patten
Tuesday Morning, April 6, 1999
Salon 11/12 (M)
The ever-decreasing dimensions of semiconductor device
features places increasing demands on developing methods to reduce undesirable
effects of surfaces. We have been developing termination chemistry for
III-V semiconductor surfaces via robustly bound, densely packed molecular
monolayers. In this talk the focus will be on the self-assembly of both
simple aliphatic and highly conjugated aromatic molecules containing S-,
Se- and Te-bearing functional groups. The range of functional groups studied
and the optimum conditions for forming structured monolayers will be discussed.
Recent results indicate that the most highly organized films appear to
be formed via Se chemistry while Te attachment requires strongly reducing
conditions. Current work is being directed towards characterizing the effects
of the organic overlayer on the electronic properties of the semiconductor
and the chemical stability of the organic/inorganic interface. Current
work is also directed towards exploring the suitability of these films
as ultrathin electron beam resists.
11:00 AM DD4.2
HOW STRONG CAN BE THE COVALENT ANCHORS OF A POLYSACCHARIDE
TO A GLASS SURFACE? Michel Grandbois , Matthias Rief, Hauke Clausen-Schaumann
and Hermann Gaub, Lehrstuhl fur Angewandte Physik, Ludwig-Maximilians-University,
Munich, GERMANY; Martin Beyer, Inst. fur Physikalische und Theoretische
Chemie, Technische Universitaet, Munich, GERMANY.
Recent developments in piconewton instrumentation allow
the manipulation of single molecules and measurements of intermolecular
as well as intramolecular forces. Using an atomic force microscope (AFM)
as force transducer we measured the force required to break a single covalent
bond in the surface anchor of a polymer chain which was covalently attached
to the AFM tip on one side and to a glass surface on the other side. The
polysaccharide amylose was used as polymer spacer, for its characteristic
force vs elongation trace, which exhibits a plateau at 275 piconewton,
allows to identify rupture events of single molecules. The rupture force
observed in our experiments is centered around 1.9 nanonewtons and is due
to the breaking of a single covalent bond in the amino-silane surface anchor
of the molecule. Furthermore, this force was compare to the force required
to pell off a polymer non covalently adsorb to the surface.
11:15 AM DD4.3
INTEGRATING ORGANIC MOLECULES TO SILICON SURFACES:AN
EFFICIENT APPROACH BASED ON Si-N AND Si-O LINKAGES. X.Y. Zhu , J.A. Mulder,
R.P. Hsung, W.F. Bergerson, University of Minnesota, Department of Chemistry,
Organic assemblies on silicon surfaces are important to
a number of cutting edge technologies: such as micro electromechanical
systems (MEMS), integrated chemical or biological sensors, and hybrid organic-silicon
electronics. We present a general strategy for the efficient assembly of
organic molecules on silicon surfaces in both vacuum environment and solution
phases via the robust Si-N or Si-O linkage. This is achieved by the reaction
between an amine or alcohol functional group and a chlorinated Si surface.
The resulting organic layers are thermally stable. This method is applicable
for the assembly of a variety of functional organic molecules.
11:30 AM DD4.4
SELF-ASSEMBLED MONOLAYERS (SAMS) ON GOLD DERIVED FROM
BIDENTATE ALKANETHIOLS. Nupur Garg, Young-Seok Shon, Ramon Colorado, Jr.,
Ramon J. Villazana and T. Randall Lee , Department of Chemistry, University
of Houston, Houston, TX.
We are developing new types of self-assembled monolayers
(SAMs) on gold from the adsorption of specifically designed bidentate chelating
alkanethiols. The chelating SAMs exhibit enhanced stabilities and/or unique
structural features when compared to those generated from normal alkanethiols.
In addition to the construction of densely packed organic thin films, the
chelating approach can be used to construct SAMs having packing structures
that contain uniquely low densities of alkyl chains. SAMs having homogeneously
mixed multicomponent interfaces can also be constructed using this methodology.
Herein, we report chelating strategies for the generation of SAMs from
three different types of adsorbates: 1,2-bis(mercaptomethyl)-4, 5-dialkylbenzenes,
2,2-dialkylpropanedithiols, and dithiocarboxylic acids. Characterization
of these SAMs by contact angle goniometry, ellipsometry, infrared spectroscopy
(FT-IRRAS), and X-ray photoelectron spectroscopy (XPS) will be presented.
11:45 AM DD4.5
INFRARED SPECTROSCOPY CHARACTERIZATION OF CHAIN-MELTING
IN BIMOLECULAR CHAIN-ASSEMBLIES SANDWICHED BETWEEN PLANAR INORGANIC NETWORKS:
LONG CHAIN SILVER THIOLATES. Atul N. Parikh , Jean-Francois Bardeau, Jaime
D. Beers, Basil I. Swanson, Chemical Science & Technology Division,
Los Alamos National Laboratory, Los Alamos, NM.
The melting of periodic, 2D chain-molecular assemblies
of a layered organic-inorganic solid, silver n-octadecyl) thiolate, is
examined using temperature dependent, Fourier-transform infrared spectroscopy
during the warm-up from -190C
to + 200C. The spectroscopic data
confirm the presence of a sharp solid-solid transition at 130C
previously assigned to a mesogenic bilayer-micellar transition preceeded
by a single gradual transition assignable to a pre-melting phenomenon which
signals the onset of hindered rotational/twisting motion about the chain-axis.
These results are interpreted in terms of the effects of proximal organic-inorganic
interface which constrains the chain melting process by frustrating essential
translational degrees of freedom.
SESSION DD5: NON-SILICATE HYBRID MATERIALS
1:30 PM *DD5.1
INORGANIC-ORGANIC COMPOSITES BASED ON FUNCTIONALIZED
SAMS. Bruce C. Bunker , Sandia National Laboratories, Albuquerque, NM;
Jun Liu, Suresh Baskaran, Glen Fryxell, Xiandong Feng, Lin Song, Peter
Rieke, Barbara Tarasevich, Gordon Graff and Allison Campbell, Pacific Northwest
National Laboratory, Richland, WA.
Chair: Thomas P. Niesen
Tuesday Afternoon, April 6, 1999
Salon 11/12 (M)
An overview is provided of research conducted at Pacific
Northwest National Laboratory in use of functionalized self-assembled monolayers
(SAMS) and surfactants to produce and enhance the performance of inorganic-organic
composites. Topics to be covered include: 1) the use of functionalized
SAMS to stimulate the nucleation and growth of ceramic phases in ``biomimetic''
processing schemes, 2) the use or organized surfactants as templates to
produce non-silica-based mesoporous materials, and 3) the use of SAMS to
tailor the surfaces of mesoporous materials for specific applications including
selective binding of heavy metals, radionuclides, and other dissolved species
and the development of low dielectric constant films for microelectronic
Sandia is a multiprogram laboratory operated by Sandia
Corporation, a Lockheed Martin Company, for the United States Department
of Energy under contract DE-ACO4-94A1185000.
2:00 PM DD5.2
SELECTIVE DEPOSITIONS OF Fe-CONTAINING OXIDE FILMS ON
MIXED SELF-ASSEMBLED ORGANIC MONOLAYERS USING MICROCONTACT PRINTING. Hyunjung
Shin , Kyongmi Lee, Geunbae Lim, Jong Up Jeon and Y. Eugene Pak, Micro
Systems Lab., Samsung Advanced Institute of Technology, Suwon, KOREA; Hyejin
Im and Eung Soo Kim, Department of Materials Engineering, Kyonggi University,
IIn situ patterning of iron-containing oxide thin layers
were fabricated via microcontact printing (CP)
and selective deposition. CP is
used to pattern two different surface moieties of self-assembled organic
monolayers (SAMs) on Au/Cr/Si substrates. An elastomeric stamp (poly(dimethylsiloxane);
PDMS) having a sub-micron size patterned relief structure were used to
transfer either hexadecanethiol (HDT) SAMs that are to sustain deposition
of iron oxide precipitates or hydrophilic SAMs (e.g. dithiothreitol (DTT)).
Selective depositions were realized through precipitation of iron oxide
phases from aqueous solutions at ambient temperature (<100C).
0.05 M of iron nitrate (Fe(NO3)29H2O)
aqueous solutions containing urea under nitric acid (pH < 2) were prepared
for selective depositions. X-ray photoelectron spectroscopic (XPS) results
showed that iron oxide precipitates (presumably
- Fe2O3) were deposited only onto hydrophilic SAMs,
but not onto HDT surfaces. Also, scanning electron microscopy (SEM) revealed
that the morphology differences of iron oxide films onto DTT surfaces deposited
by the CP and directly from the
solutions. Auger electron microscopy and atomic force microscopy were used
to characterize definition of micron sized patterns of iron oxide thin
2:15 PM DD5.3
SYNTHESIS AND CHARACTERIZATION OF TITANIA AND VANADIA
THIN FILMS AT ORGANIC SELF-ASSEMBLED MONOLAYERS. Thomas P. Niesen , Jurand
Wolff, Joachim Bill, Fritz Aldinger, Max-Planck-Institut für Metallforschung
and Institut für Nichtmetallische Anorganische Materialien, Universitaet
Stuttgart, Stuttgart, GERMANY.
Self-assembled monolayers (SAMs) on single-crystal Si
wafers have been used as substrates for the deposition of oxide thin films.
The organic surface has been shown to be effective for promoting the growth
of films from aqueous solutions at low temperatures. Recent new results
will be presented, including the deposition and characterization of titania
and vanadia films. Titania films have been synthesized by hydrolysis of
TiCl4 in aqueous HCl solutions at 80C
on sulfonated SAMs. In presence of H2O2, the thermal
stability of the solutions is enhanced by complexation of free titanium
ions. Therefore, uniform films were achieved at higher pH compared to previous
research, combined with higher deposition rate. Vanadium-containing films
have been formed by hydrolysis and condensation of H3VO4
solutions on Si wafers coated with -NH2 SAMs, likewise at 80C.
The as-deposited films consisted of V2O5xH2O
in form of turbostratic layers with intercalated water molecules and could
be transformed to crystalline vanadia by annealing in air. As-deposited
and annealed films were characterized by a variety of spectroscopic and
microscopic techniques, including ellipsometry, rutherford backscattering
spectroscopy, atomic force microscopy and transmission electron microscopy,
to determine thickness, topography, microstructure and chemical composition
of the films. Based on these and previous results, the current understanding
of the film formation will be discussed.
2:30 PM DD5.4
DEPOSITION OF TIN (IV) OXIDE CERAMIC FILMS ON ORGANIC
SELF-ASSEMBLED MONOLAYERS. Sitthisuntorn Supothina, Mark R. De Guire ,
Arthur H. Heuer, Case Western Reserve University, Department of Materials
Science and Engineering, Cleveland, OH; Thomas P. Niesen, Joachim Bill,
Fritz Aldinger, Max-Planck-Institut fuer Metallforschung, Pulvermetallurgisches
Laboratorium, Stuttgart, GERMANY.
Nanocrystalline thin films of tin (IV) oxide (cassiterite)
have been deposited from aqueous solutions of tin (IV) chloride and hydrochloric
acid at 80 degrees Celsius. Substrates were 100 silicon wafers, with and
without silanol-anchored organic self-assembled monolayers (SAMs). Both
static and flowing solutions have been used. The thickness of the films
from static solutions is limited to about 50 nm, whereas films with thicknesses
of several hundreds of nm have been grown from flowing solutions. The films
are pore- and crack-free, adherent and microstructurally uniform on both
SAM-covered and bare (oxidized, hydrolyzed) silicon wafers. The role of
the substrate in the deposition process will be discussed, as well as that
of the flow rate and configuration of the deposition chamber. Characterization
of the films using transmission electron microscopy, Rutherford backscattering
spectroscopy, atomic force microscopy, and x-ray photoelectron spectroscopy
will be discussed.
3:15 PM *DD5.5
ADDITIVE FABRICATION OF MATERIAL MICROSTRUCTURES USING
ORGANIC THIN FILM TEMPLATES. Ralph G. Nuzzo , David Payne, Martin Erhardt,
University of Illinois at Urbana-Champaign, Department of Chemistry, Urbana,
Additive fabrication involves the directed construction
of thin-film microstructures. In this talk I will describe the construction
of a variety of thin film microstructures and devices, including waveguides,
MOSFET and TFT transistors, ferroelectric capacitors, and metal-silicide
Schottky diodes, using non-photolithographic patterning methods. Of particular
interest in this work is the combined use of selective deposition chemistries
with soft-lithographic patterning methods to facilitate the construction
of complex multilayer structures. The current status of progress in these
areas will be described.
3:45 PM DD5.6
SYNTHESIS OF TRANSITION-METAL-OXIDE MESO-STRUCTURE THIN
FILMS (II). H.S. Zhou , I. Honma, Energy Division, Electrotechnical Laboratory
(ETL), AIST, Tsukuba, JAPAN.
Self-assembly organic-inorganic molecules into highly
order mesostructured architecture have attracted increasing attention because
these materials provide a rich source for scientific researches and technological
applications. However, for electronic and optical application, it is very
important to control the material's morphology from powder to thin film.
We already reported the synthesis of oriented V2O5,
Fe2O3, Nb2O5 and TiO2
transition-metal-oxide meso-structure films with surfactants by a spin
coating method. Here we present that the morphologies' transformation of
V2O5 and TiO2 transition-metal-oxide meso-structure
films. We used the precursor of vanadium tri-n-propoxide oxide, 1-propanol
and the surfactant of hexadecyltrimethylammonium bromide (C16TMA) to synthesized
V2O5 meso-structure film, and used the titanium tetra-iso-propoxide
(TTIP), 2-propanol and the surfactant of monododecylphosphate (MDP) for
TiO2 meso-structure film. X-ray diffraction patterns show that
both the films oriented in lamellar structures at the first stage. But,
it can transfers, according to the aging time at room tempera- ture, from
a lamellar or double lamellar phase to a mixture of lamellar and cubic
or other mixture phases. The lamellar structures of TiO2 meso-structure
films are collapsed by decomposition of surfactants on about 300C heat
treatment for 2 hours. We also investigated the differential thermal analysis
(DTA), thermogravimetry (TG) and IR spectra of TiO2 meso-structure
4:00 PM DD5.7
THE SYNTHESIS OF ORGANIC VANADIUM OXIDE LAYERED STRUCTURES.
M. Stanley Whittingham , Peter Zavalij, Katana Ngala and Arthur Dobley,
Materials Research Center and Chemistry Department, State University of
New York at Binghamton, NY.
The formation of organic-inorganic hybrid materials by
hydrothermal synthesis has been explored systematically in the case of
vanadium oxides. The organic ion or chelating molecule has a profound effect
on the structure formed, as also does the pH of the reaction medium and
the nature of the reaction medium itself. Recent experiments using the
small spherical and very stable tetramethylammonium ion, the hydrogen bonding
methylammonium ion, the triethylammonium ion as well as long surfactant
ions will be described. A range of structures were formed in these experiments,
ranging from one-dimensional inorganic strings, through inorganic layers
and tunnel compounds to three-dimensional lattices. These have been characterized
and the beginnings of a rational approach to synthesizing such compounds
is being seen. This work is being supported by the National Science Foundation,
Division of Materials Research.
4:15 PM DD5.8
SOLVOTHERMAL SYNTHESES AND CHARACTERIZATIONS OF ONE-DIMENSIONAL
AND TWO-DIMENSIONAL ORGANO-TEMPLATED VANADIUM ARSENATE AND PHOSPHATE PHASES.
Yu-Min Tsai, Li-Hsun Hung, Sue-Lein Wang , Dept of Chemistry, National
Tsing Hua University, Hsinchu, TAIWAN.
Solvothermal reactions of the piperazine/V/X/O (X = As,
P) systems were investigated. Variations in temperature, solvents, stoichiometries
of reactants, and starting pH values of the reaction solutions resulted
in the isolation of four novel phases: (C4N2H12)2(V2O3)2(AsO4)(HAsO4)(H2AsO4).4H2O
(3), and (C4N2H12)[V2O3(HPO4)(PO4)]
(4), respectively. Phases 1, 2 and 3 are vanadyl(IV) compounds. They adopt
different 1D chain structures. The chains in 1 and 2 contain a common building
unit, edge-sharing V2O10 bioctahedra which are linked
by arsenate tetrahedra in different manners. In the structure of 3, chains
are constituted by four-connected (-V-O-P-O)2 units which can
be thought as derived from the well-known structure of the VOPO4.2H2O.
Each of the V centers are as well coordinated by one oxalate group which
is acting as a bidentate ligand. It is the first vanadium oxalatoarsenate
compound ever reported in the literature. Phase 4 is a mixed-valence vanadyl(IV,V)
compound. It adopts a layer structure in which two kinds of V-O polyhedra
with different valence on V centers coexist. Each layer is formed of two
types of infinite chains interlinked by PO4 tetrahedra- one
contains corrner-sharing VVO5 square pyramids
and the other contains isolated VIVO6 octahedra
in four-connected units similar to that in 3. The unified synthetic strategy,
crystal structures, structrual relationship, thermal analyses, and magnetic
properties of these new phases will be presented in detail.
4:30 PM DD5.9
A NEW ROUTE TO PREPARE HARD AND ANTI-SCRATCHING COATINGS
AT ROOM TEMPERATURE. Yanjing Liu, NanoSonic, Richard O. Claus , Dept of
Electric and Computer Engineering, Dept of Material Science and Engineering,
Virginia Tech, VA; Aprillya Rosidian, Dept of Material Science Engineering,
Virginia Tech, VA; Tingying Zeng, Dept of Electrical Engineering, Virginia
A new method for the preparation of hard and anti-scratching
coatings at room temperature has been developed, based on the layer-by-Layer
electrostatic self-assembly (ESAM) technique. Highly homogeneous and several
micron thick coatings of nanoparticles including ZrO2, Al2O3,
SiO2, and ZrO2/ Al2O3 have
been prepared on plastics, glass and other curved substrates. UV-vis spectroscopy,
ellipsometry, atomic force microscopy, and nanoindentation tester have
been used to characterize the homogeneity, thickness, morphology, and mechanical
properties before and after sintering.
4:45 PM DD5.10
REAL-TIME ANALYSIS OF CRYSTALLIZATION AT SURFACES USING
LUMINESCENCE MICROSPECTROSCOPY. Michael J. Lochhead , Univ of New Hampshire,
Dept of Chemical Engineering, Durham, NH; Lara Touryan, Viola Vogel, Univ
of Washington, Dept of Bioengineering, Seattle, WA.
Organic templating of inorganic nano- and microstructures
is a promising new approach to advanced hybrid materials. Continued development,
however, will rely on an improved understanding of structure-property-processing
relations, which in turn will rely on improved methods for characterizing
nucleation and growth events in real time. In the current work we use a
technique called luminescence microspectroscopy (LMS) that combines the
spatial resolution of optical microscopy with the structural sensitivity
of rare earth ion spectroscopy. Using europium(III) as a luminescent probe,
the technique allows real-time analysis of the evolving crystals while
they are in contact with their aqueous growth solutions. Optical imaging
provides morphology assessment at micrometer scales while luminescence
spectroscopy provides probe ion local bonding information at molecular
scales. In the current work, we use LMS to characterize the morphology
and phase of biominerals such as calcium oxalate during the early stages
of crystal formation. Spatially resolved luminescence spectra are obtained
for micrometer-scale crystallites. Beyond the micrometer scale, LMS holds
promise for providing spatially resolved spectra from templated crystals
and structures smaller than the limits of optical resolution. Technical
challenges associated with in-situ nanocrystal characterization will be
SESSION DD6: MESO-, MICRO-, AND MACROPOROUS HYBRIDS
8:30 AM *DD6.1
TEMPLATED SYNTHESES OF POROUS METAL OXIDES AND HYBRID
MATERIALS. Brian Holland, Christopher Blanford, Myong Hoon Lim, Andreas
Stein , University of Minnesota, Department of Chemistry, Minneapolis,
Chair: Roger A. Assink
Wednesday Morning, April 7, 1999
Salon 11/12 (M)
Routes of templating inorganic and hybrid solids with
periodic pore structures covering a wide range of pore sizes will be discussed.
The syntheses are based on molecular and supramolecular templates for the
nanometer range, and macromolecular templates for the submicrometer range.
Supramolecular templating with surfactant aggregates includes direct syntheses
of mesoporous sieves with covalently attached organic surface groups and
hydrothermal syntheses of mesoporous sieves with trapped functional organic
molecules, such as porphyrins. Macromolecular templating with polystyrene
spheres as templates has led to highly periodic macroporous oxides of Si,
Ti, Zr, Al, W, Fe, Sb, and a Zr/Y mixture, as well has aluminophosphates
and hybrid compositions. These products were synthesized from readily available
alkoxide precursors and consisted of periodic, interconnected networks
of polycrystalline or amorphous wall with monodisperse submicron pores.
Depending on the technique of template removal, the crystallographic phase
of the walls could be controlled for some compositions. In the case of
silicates, products with bimodal distributions of meso- and macropores
were obtained. It is expected that the syntheses can be adapted to many
other metal oxides, phosphates, or chalcogenides. As a result, one can
forsee an impact on diverse applications that would benefit from the porosity,
low density, and order of these novel ceramic structures, such as quantum
optics, chromatographic stationary supports, large molecule catalysts,
host materials for biological molecules, porous electrodes, metal-ceramic
composites, or thermal insulators.
9:00 AM DD6.2
HIERARCHICALLY ORDERED POROUS OXIDES. Peidong Yang ,
Dongyuan Zhao, Bradley F. Chmelka, Galen D. Stucky, Department of Chemistry,
Chemical Engineering, University of California, Santa Barbara, CA; Tao
Deng, George M. Whitesides, Department of Chemistry and Chemical Biology,
Harvard University, Cambridge, MA.
A continuing challenge for materials chemists is the ability
to create multifunctional composite structures with well-defined superimposed
structural order from nanometer to micrometer length scales. Porous silica,
niobia, and titania materials with three-dimensional structures ordered
over multiple length scales were prepared by combining micromolding, polystyrene
sphere templating and cooperative self-assembly of inorganic sol-gel species
with amphiphilic triblock copolymers. The resulting materials show hierarchical
ordering over several discrete and tunable length scales ranging from 10
nm to several micrometers. The respective ordering structures can be independently
modified by choosing different mold patterns, latex spheres and block copolymers.
The examples presented demonstrate the compositional and structural diversities
that are possible with this simple approach.
9:15 AM DD6.3
INFLUENCE OF THE PREPARATION CONDITIONS ON THE STRUCTURE
OF ORGANICALLY-MODIFIED POROUS SILICATES. Valérie Goletto, Sophie
Besson, Valérie Dagry, Florence Babonneau , Chimie de la Matiëre
Condensée, UPMC-CNRS, Paris, FRANCE.
The discovery of the MCM series of mesoporous materials
has opened up the way to entirely new mesostructured materials, with large
surface areas and uniform distribution of pores. Many applications such
as adsorption, ion exchange, catalysis and sensing, require the materials
to have specific surface properties. One way to introduce oragnic functions
at the silica surface is a one-pot synthetic approach, as described in
this paper. Organically-modified porous silicates have been prepared from
various trialkoxysilanes, RSi(OR')3 and tetraethoxysilane as
hybrid precursors, and cetyltrimethylammonium bromide (CTAB) as structuring
agent. Structure of the final samples have been characterized by X-ray
diffraction and porosity measurements, as well as 29Si and 13C
MAS-NMR experiments. The nature of the organic group plays an important
role on the extent of mesoscopic order, and different behaviors are observed
depending on whether basic or acidic conditions are used.
10:00 AM DD6.4
HYBRID MESOPOROUS MATERIALS AS HOSTS FOR POLYMER COMPOSITES.
Karin Moller , Thomas Bein, Department of Chemistry, Purdue University,
West Lafayette, IN; Reinhard X. Fischer, Department of Geosciences, University
of Bremen, Bremen, GERMANY.
Hybrid mesoporous materials based on MCM-41 and SBA-type
periodic mesoporous hosts are synthesized at room temperature by co-condensation
of 3(trimethoxysilyl)propyl methacrylate (TMSiPMA) and tetramethylorthosilicate
(TMOS) in the presence of cetyltrimethylammonium chloride or poly(ethylene
oxide)- poly(propylene oxide)- poly(ethylene oxide) triblock copolymers.
Highly ordered mesoporous materials are obtained after template removal
through solvent extraction as shown by x-ray diffraction and transmission
electron microscopy. Alternatively, grafting of TMSiPMA and 3-(glycidoxy)propyl
trimethoxysilane is performed in a post synthesis step to introduce functionality
into the mesoporous hosts. The reactivity of the grafted methacrylate carbon-carbon
double bonds is demonstrated by their complete consumption during bromination.
The presence of the functional groups within the mesoporous channels is
exploited for the formation of inorganic/organic composites on the molecular
level: the intra-pore grafted methacrylate groups are polymerized with
adsorbed methyl methacrylate monomer (MMA) to form occluded PMMA filaments.
10:15 AM DD6.5
NON-IONIC SURFACTANT AND BLOCK COPOLYMER TEMPLATED MESOPOROUS
SILICA FILMS THROUGH EVAPORATION-INDUCED SELF-ASSEMBLY. Hongyou Fan , Yunfeng
Lu, Frank van Swol, C. Jeffrey Brinker, Sandia National Laboratories, and
the University of New Mexico/NSF Center for Micro-Engineered Materials,
The Advanced Materials Laboratory, Albuquerque, NM.
Transparent, defect-free films with controlled pore structure
and surface chemistry are of interest for applications such as membranes,
sensors, optical hosts, and low K dielectrics. We reported a rapid surfactant-templated
approach to prepare a family of mesophase silica films with pore size less
than 2 nm. Starting with an oligomeric silica sol plus CTAB, we exploited
surfactant enrichment during dip-coating to obtain a family of films exhibiting
hexagonal, cubic, or lamellar mesostructures. In this presentation, nonionic/amphiphilic
block copolymers have been used to produce mesoporous films. A potential
advantage of these nonionic polymer templates is the formation of thicker
silica walls resulting in greater thermal and mechanical stability, as
well as avoidance of mobile ions that would degrade dielectric performance.
In addition, block copolymers template much larger pore size. For example,
using Pluronic triblock copolymer (PEO)20(PPO)70(PEO)20,
we produced mesoporous thin film with cubic phase. The pore size, porosity,
and surface area of the film are 7 nm, 50%, and 910 m2/g respectively.
SAXS, TEM, and surface acoustic wave(SAW) sorption techniques are used
to characterize the microstructures of the films. Hybrid organic/inorganic
mesoporous films are also prepared by co-condensation of TEOS + RSi(OR)3,
where R is a hydrophobic non-hydrolyzable ligand
10:30 AM DD6.6
THERMAL STABILITY OF STRUCTURALLY CONTROLLED LAMELLAE,
CUBIC AND HEXAGONAL MESOPOROUS SILICATE THIN FILMS. Itaru Honma , *D. Kundu
and H.S. Zhou, Energy Division, Electrotechnical Laboratory, AIST, Umezono,
Tsukuba, Ibaraki, JAPAN; *Central Glass and Ceramic Research Institute,
Mesostructured silica-surfactant composites in the thin
film form are synthesized using cationic surfactant and tetraethyl orthosilicate
(TEOS) derived sols via a novel co-assembly process on inorganic surfaces
or air/water interfaces with lamellae or hexagonal structure through changing
the silica to surfactant ratio. Porous silica films having ordered structure
which may find applications in the field of sensors, catalyst etc were
formed via the removal of surfactant by thermal treatment. Thermal stability
of the composite films of ordered structure is supposed to be an important
factor from the view point of application. In this paper, we report here
about a simple process to synthesize among lamellae, cubic and one-dimensional
hexagonal (1-dH) silica-surfactant composite films on ordinary slide glass
by spin coating process. The process provides a systematic changes of the
mesophase of lamellae, cubic and hexagonal by surfactant compositions.
Thermal decomposition of the surfactant from the composite films has been
studied; The surfactant in the mesopore was seen to remove gradually from
the composite films in the temperature range 100C
- 200C and finally decomposed
at 250C. The removal of surfactant
destroyed the highly ordered lamellae structure, however, cubic and one-dimensional
hexagonal (1-dH) films keep its structure after the calcination of the
pores. Thus, highly homogeneous films having cubic and hexagonal pore structure
can be generated via the decomposition of surfactant.
10:45 AM DD6.7
SILICEOUS MESOSTRUCTURED CELLULAR FOAMS SYNTHESIZED BY
A MICROEMULSION TEMPLATING ROUTE. Patrick Schmidt-Winkel , Wayne W. Lukens
Jr., Dongyuan Zhao, Peidong Yang, David J. Pine, Bradley F. Chmelka, Galen
D. Stucky, UCSB, Dept of Chemistry, Materials Research Laboratory, Dept
of Chemical Engineering, Santa Barbara, CA.
Porous materials with controllable large pore sizes have
potential applications as hosts for chemical reactions and for separations
involving big molecules. Mesoporous materials are attractive in this respect
as they cover pore sizes from 20 to 500 .
We present siliceous mesostructured cellular foams (mesocellular foams,
MCFs) made up of uniformly sized spheres that are synthesized by a microemulsion
templating route. The MCFs represent continuous pore systems with narrow
pore size distributions and large surface areas up to 900 m2/g.
Uniform spherical cells up to 36 nm in diameter are three-dimensionally
interconnected through uniform windows measuring 7-18 nm across. Thermodynamically
stable oil-in-water microemulsions are prepared by adding an organic co-solvent
(oil) to a dilute solution of a non-ionic triblock copolymer surfactant
in aqueous acid. The size of the cells can be controlled by changing the
amount of added organic co-solvent during the formation of the templating
microemulsion. Adding small amounts of fluoride to the reaction mixture
enlarges the window size independently of the cell size and improves the
structural homogeneity of the MCF materials. In addition, fluoride addition
gives rise to the formation of strut-like matrix arrays that resemble aerogels
with the benefit of well-defined pore sizes combined with a significantly
11:00 AM DD6.8
A NOVEL METHOD FOR MAKING MACROPOROUS BULK GELS AND THIN
FILMS BY EMULSION TEMPLATING. G. Subramanian , Materials Department, University
of California Santa Barbara, CA; V.N. Manoharan, Dept. of Chemical Engineering,
University of California, Santa Barbara, CA; A. Imhof, Van der Waals-Zeeman
Instituut, Universiteit van Amsterdam, Amsterdam, NETHERLANDS; D.J. Pine,
Chemical Engineering and Materials Departments, University of California,
Santa Barbara, CA.
Ordered macroporous ceramics such as silica and titania
have been synthesized by using alkoxide precursors employing either monodisperse
emulsion droplets  or polystyrene latex particles as templates [2, 3].
The emulsion templating method offers several advantages over the polystyrene
latex particles including easy removal of the template and the ability
to produce large monoliths. Removal of the latex particle templates by
heat treatment invariably results in structurally fragile materials that
fracture into small (< 0.5 mm) pieces. In this paper we describe a novel
method of making macroporous bulk gels and thin films of silica using emulsion
templating. Bulk gels with dimensions greater than 1 cc can be easily produced.
The method involves use of a colloidal sol of silica instead of the usual
alkoxide precursors to produce gels. Starting with uniform emulsion droplets
and a stable colloidal sol of silica spheres (80-100 nm diameter), we were
able to produce macroporous bulk gels and thin films in which the silica
particles consolidate around the emulsion template on evaporation of water
during drying. The emulsion template was then removed by washing with alcohol
leaving macropores in the material. Subsequent heat treatment could then
be used to densify the sol particles to produce ordered macroporous silica.
Monodisperse emulsion droplets of the required size were made by controlled
swelling of monodisperse polystyrene latex particles with organic solvents
such as decalin. Good control of the pore size and applicability to other
colloidal systems such as titania and zirconia make this method attractive
for synthesizing macroporous materials.
1. Imhof, A. and D.J. Pine (1997) Nature 389 (6654):
2. Holland, B.T., C.F. Blanford, et al. (1998) Science
281: 538-540. 3. Wijnhoven, J.E.G.J. and W.L. Vos (1998) Science 281: 802-804.
11:15 AM *DD6.9 APPLICATIONS OF LOW DENSITY AND
HIGH SURFACE AREA ORGANIC-INORGANIC HYBRID MATERIALS. Douglas M. Smith
, Steven Wallace, Teresa Ramos, Vinay Menon, NanoPore Incorporated, Albuquerque,
The combination of high surface area and high porosity/low
density are important material properties for a number of applications.
One rapidly growing example is advanced thermal insulation where densities
in the range of 50 to 150 kg/m3 are required but high surface areas (>500
m2/g) are also necessary. The high surface area is necessary in order to
achieve small pore sizes as to enable reduced gas phase conduction. Organosilicates
offer the advantage for that application of both excellent thermal performance
and hydrophobicity. At the opposite end of the value spectrum is low dielectric
constant materials for semiconductor interconnects. Low density is desired
to lower dielectric constant but pores must all be small (<10 nm) and
the material must be hydrophobic. The development of hybrid materials for
these and other applications will be presented. In addition, further materials
development opportunities for these applications will be highlighted.
SESSION DD7: HYBRID ELECTROCHEMISTRY, PHOTOCHEMISTRY,
PASSIVATION, AND SENSING
1:30 PM *DD7.1
MESOPOROUS HETEROJUNCTIONS AND DYE SENSITIZED NANOCRYSTALLINE
SOLAR CELLS. Michael Graetzel , Swiss Federal Institute of Technology,
Institute of Photonics and Interfaces, Lausanne, SWITZERLAND.
Chair: Martin Mennig
Wednesday Afternoon, April 7, 1999
Salon 11/12 (M)
The salient features of mesoporous junctions composed
of an n-type nanocrystalline oxide film the porous network of which is
filled with an amorphous p-type organic semiconductor will be discussed.
Of particular interest is the case of the dye sensitized heterojunction
solar cell based on nanocrystalline TiO2 and the novel organic
hole transport material 2,2',7,7'-tetrakis-(N,N'-di-p-methoxyphenylamine)-9,9-spirobifluorene
(spiro-OMeTAD). A monolayer of charge transfer sensitizer present at the
junction is used to harvest sunlight and to inject an electron in the conduction
band of the oxide. The dye is regenerated by hole injection in the spiro-OMeTAD.
The dynamics of this double injection process at the solid jucntion has
been investigated by laser photolysis. Light induced charge separation
occurs in the femto to picosecond time domain. By contrast the unwanted
recombination of electrons injected in the inorganic oxide film with the
holes injected in the organic semiconductor is four to five orders of magnitude
slower. Solar cells based on this new type of dye-sensitized organic/inorganic
hybride heterojunction have been developed and exhibit a strikingly high
photon to current conversion effiency.
2:00 PM DD7.2
PHOTOELECTROCHEMICAL PROPERTIES OF SELF-ASSEMBLED MULTILAYERS
OF ORGANIC-INORGANIC THIN FILMS AND THEIR USE FOR CATALYSIS. Feras Abdelrazzaq
, Raymond Kwong, Alexandre Dokoutchaev, Venkatesan Krishnan, Mark Thompson,
Department of Chemistry, University of Southern California, Los Angeles,
We have previously examined the photocurrent generation
in metal bisphosphonate multilayer thin films (Nature 1996, 380, 610-612).
In this paper we will describe the synthesis and characterization of metal
bisphosphonate and metal dithiolate thin films composed of quinones and
viologen, based acceptors layers and porphyrin, hydroquinone, phenylene
diamine, and dihydroxynaphthalene as donor layers. Zirconium bisphosphonate
multilayers of these novel compounds and other metal dithiolate multilayers
(-SRS-M-SRS-, R= porphyrin; M=Cu) were grown on different substrates (e.g.
Au, Si, etc.) and were studied by AFM, UV-Vis, Fluorescence Spectrometry,
Ellipsometry and Cyclic Voltametry. These photoelectroactive films produced
photocurrent with a quantum yield of (1-5%) based on absorbed light. Our
method of film growth provides control over both the structure and the
composition of multilayer films leading to efficient photoinduced charge
separation. These photoelectrode generated photocurrent when irradiated
with ultraviolet and visible light. The photoelectrode can then be repeatedly
cycled giving the same current with no major degradation. In these experiment
we shift the active wave length region of these devices by choosing the
appropriate redox species that absorbs in the desired region. Interestingly,
we find that incorporating these redox active species in a cascade type
arrangement (according to their redox potentials and optical properties)
resulted in an increase in the quantum yield and increase of electron transport
through the material. When these photoactive multilayers were grown on
silica-supported colloidal metal particles (e.g. Pt, Pd) they have been
utilized for photochemical hydrogen production from water. The electrochemical
and photochemical properties of these films will be discussed.
2:15 PM DD7.3
SYNTHESIS OF SILICA/PEO NANO-HYBRIDS PROTONIC CONDUCTING
MEMBRANE THROUGH SOL-GEL PROCESSES. Itaru Honma , Electrotechnical Laboratory,
AIST, Tukuba, JAPAN; Y. Takeda, Kougakuinn University, Tokyo, JAPAN and
J.M. Bae, NEDO, JAPAN.
In this paper, the synthesis of new protonic conducting
organic/inorganic nanocomposites electrolyte membrane is reported and the
conductive properties at the elevated temperature with various humidities
have been investigated. The electrolyte membrane is composed of nano-level
ceramic/polymer composites which is synthesized through sol-gel processes.
Silica (SiO2)/Polyethyleneoxide (PEO) organic/inorganic nanocomposite
(SPC) are remarkable family of isotropic, amorphous, nanocomposite materials.
The rigid silica domain in the composite results in high strength and temperature
toughness while the PEO chain serve to provide flexibility and melt processibility.
The SPC doped with acidic surfactant of monododecylphosphate (MDP) at different
rate are casted from the mixed solution and the membrane are dried at ambient
temperature. The Silver electrode are attached on both sides of the membrane
and protonic conductivities are measured at elevating temperatures and
various humidities. Protonic conducting properties of SPC doped with MDP
in the temperature range from 60C to 160C with humidifier temperature higher
than that of the operating cell by 15C for hydrogen and 10C for oxygen
lines. The protonic conductivity decreases with elevating temperature from
5 x 10-3 S/cm at R.T. to approximately 10-4 S/cm
at 160C, which is highly conductive as an organic/inorganic hybrid membrane..
2:30 PM DD7.4
NANOSTRUCTURAL LITHOGRAPHY VIA PHOTO-INITIATED PHASE
TRANSFORMATION OF SILICA-SURFACTANT ASSEMBLIES. Dhaval Doshi 1,
Nicola Huesing2, Hongyou Fan1, Alan Hurd3,
C. Jeffrey Brinker1,3, 1The University of New Mexico/NSF
Center for Micro-Engineered Materials, Albuquerque, NM; 2Technische
Universitat Vienna, AUSTRIA; 3Sandia National Laboratories,
Cooperative self-assembly processes of inorganic species
and amphiphilic molecules have experienced major advances over the past
six years. Various pathways have been explored to access a wide spectrum
of mesostructured materials with tunable pore sizes and arrangements and
good compositional control. A variety of macro- and microstructures have
been synthesized such as powders, fibers, monolith, thin films, hollow
and transparent hard spheres and aerosol particles which find applications
in catalysis, membrane separation, sensors, optoelectronics, and as novel
nanomaterials. However, the ability to design these materials with spatially
controlled combinations of different mesophases or compositions, and therefore
different properties, would greatly enhance their utility as nanofunctional
surfaces. We present a simple lithographic procedure which allows a deliberate
control of structure and properties of a meso-ordered silica film through
optical mediation. This nanostructural lithography process exploits the
pH sensitivity of supra-molecular self-assembly. Through addition of a
photoacid or base generator in the coating sol along with surfactant and
silica, dip coating results in the self-assembly of continuous, ordered
photosensitive films. UV exposure through a mask produces local pH changes,
inducing mesostructural phase transitions. Two surfactant systems (CTAB
and Brij 56) are studied. X-ray diffraction, transmission and scanning
electron microscopy, optical microscopy, ellipsometry, MAS-NMR and atomic
force microscopy were used to characterize the patterned nanostructured
surfaces. Additionally, lithographically patterned films are also formed
by in situ polymerization of organic molecules within the silica-surfactant
assembly leading to a true inorganic-organic nanocomposite material.
3:15 PM DD7.5
SOL-GEL SYNTHESIS OF MOLYBDENUM OXIDE/POLY- PYRROLE HYBRIDS.
Winny Dong and Bruce Dunn, UCLA, Los Angeles, CA.
An advantage of inorganic/organic materials is that each
constituent can contribute to a specific property. The goal of synthesizing
molybdenum oxide/polypyrrole hybrid aerogels is to produce a cathode material
for rechargeable lithium batteries. Molybdenum oxide provides the lithium
intercalation capacity while polypyrrole provides the high electrical conductivity.
This material can be made as aerogels to further increase Li capacity through
its high surface area. Molybdenum oxide/polypyrrole hybrid aerogels and
xerogels have been synthesized through the sol-gel method. Simultaneous
polymerization where oxidation of the pyrrole occurs with the reduction
of the molybdenum leads to a molecular level composite. This hybrid shows
increased conductivity (2E-2 S/cm) over molybdenum oxide gels (5E-4 S/cm).
The increased conductivity has been achieved without the use of oxidizing
agents. The relationship between synthesis and conductivity will be discussed.
An increase in lithium intercalation capacity has also been observed (from
1.1 Li/Mo to 1.6 Li/Mo).
3:30 PM DD7.6
IN SITU INTERCALATION/POLYMERIZATION OF MELANIN INTO
VANADIUM PENTOXIDE. H.P. Oliveira , C.L.P.S. Zanta, A.C. Galina, USP, DQ-FFCLRP,
Ribeirao Preto, BRAZIL; C.F.O. Graeff, USP, DFM-FFCLRP, Ribeirao Preto,
The possibility of combining the properties of organic
and inorganic compounds in a unique material is an old challenge. These
new materials, considered as innovative advanced materials, promise new
applications in many fields such as optics, electronics, ionics, mechanics
and biology. V2O5 xerogel have interesting conducting
as well as electrochemical properties like the laminar (or 2D ) structure
adequate for intercalation reactions. Melanin is a bio-polymer with interesting
properties like the high photo-absorption in a wide range of photo energies
as well as good photoconductivity. The films were obtained by inserting
3,4-dihidroxi-fenialanina (DOPA) in a solution with HVO3, which
suffered a oxidative polymerization/intercalation process, forming a gel
with a dark blue metallic color. The films were characterized using UV
transmission spectroscopy, FTIR, ESR, X-ray diffraction, and cyclic voltammetry
as well as spectroelectrochemistry. The X-ray diffractograms indicate that
the laminar structure of the V2O5 is preserved but
the inter-planar space increased from 1.18 nm to 1.38 nm. The FTIR and
ESR spectra confirms that the V2O5 structure is preserved,
however the presence of melanine induces the reduction of V ions to VIV.
The increase in the inter-planar spacing is observed to increase the stability
and reproducibility of the electrochemical insertion/de-insertion of Li+.
This increase in stability is also observed in the electrochromic properties
of the film, which are fully reproducible even after more than 30 oxidation-reduction
cycles. The presence of melanin induces the appearance of a new broad absorption
band in the reduced state (-0.9V) at around 750 nm attributed to a charge
transfer from V(IV) to O, in good agreement with the ESR results.
3:45 PM DD7.7
SYNTHESIS AND CHARACTERIZATION OF PIPERIDINE INTERCALATES
OF AND -HAFNIUM
PHOSPHATE. M. Luz Rodrigues, Luisa M. Barcina, Maria A. Villa-Garcia ,
Ricardo Llavona, Marta Suarez, Julio Rodriquez, Departamento de Quimica
Organica e Inorganica, Facultad de Quimica, Universidad de Oviedo, Oviedo,
The Intercalation chemistry of
and - metal (IV) phosphates
is dominated by the presence in the interlayer region of Bronsted acid
groups. Species with sites that can be protonated are preferred guests.
In the case of the amines, the intercalation reaction is driven by an acid-base
interaction between the P-OH groups of the layer and the amino groups.
For a given guest the intercalation can lead to the formation of various
organic-inorganic hybrid materials, that differ in composition and interlayer
distance. This work describes the intercalation reactions of piperidine
-hafnium phosphate were equibrated during 5 days, with aqueous solutions
of piperidine containing from 0.5 to 10 mmol amine/g of phosphate. Piperidine
intercalates were also obtained by exposing
-hafnium phosphate to an atmosphere saturated with piperidine vapour.
The organic-inorganic intercalates were characterized
by chemical and thermal analysis, X-ray diffraction and IR Spectroscopy.
The results obtained show that the intercalation process
of piperidine in -HfP in aqueous
solution takes place with the formation of only one phase of composition
H2O and d002 = 13.3 .
No intermediates phases have been detected and the amine is not able to
saturate the material. This result is analogous to that obtained when the
intercalation process occurs with piperidine in vapour phase; different
results were obtained when the intercalation process takes place in pure
amine, where saturation is reached with formation of the Hf(HPO4)2
H2O(d002 = 15.4 .
In -HfP the final phase obtained
in aqueous solution is the same than that obtained when the process is
carried out in pure amine, Hf(PO4) (H2PO4)
2H2O (d002= 18.0 )
however the process takes place with the formation of an intermediate phase
of composition Hf (PO4) (H2PO4)
2H2O (d002 = 13.9
that was also detected when the intercalation process occurs in vapour
4:00 PM DD7.8
SYNTHESIS OF NANO-SCALE ZEOLITE FILMS FOR VAPOR-SENSING
DEVICES. Svetlana Mintova , Shangyi Mo and Thomas Bein, Department of Chemistry,
Purdue University, West Lafayette, IN.
Seed-based synthesis methods for ultra-thin films of different
molecular sieves have been developed. The different pore sizes and large
specific surface areas of BEA, MFI, LTA and AFI type colloidal molecular
sieves synthesized on sensor substrates make them suitable materials for
the design of sensors with high selectivity and sensitivity. The dimensions
of the colloidal particles are in the range of 40-100 nm, which leads to
the formation of ultra-thin films with controlled thickness. Quartz crystal
microbalances (QCM) were used as substrates for the deposition of zeolite
films with different thickness by varying the adsorption conditions of
colloidal zeolite seeds, and the temperature and duration of subsequent
hydrothermal treatments. In very thin films, most of the crystalline materials
are oriented on the sensor surfaces. Computer-controlled sorption measurements
on sensor devices coated with ultra-thin and very stable zeolite films
demonstrate high molecular shape selectivity based on the molecular sieving
capabilities of the zeolites. The equilibration rates of different vapors
are controlled by the nature of the molecular sieve, and by the thickness
and texture of the films. Fast response and excellent reversibility were
obtained for thin colloidal layers, which show remarkable sensitivity at
low vapor concentrations.
4:15 PM DD7.9
CORROSION RESISTANT AND HIGH TEMPERATURE COATINGS FROM
PRECERAMIC POLYMERS. Y.D. Blum , S.M. Johnson, D.B. MacQueen and C. Kanazawa,
SRI International, Menlo Park, CA.
Corrosion resistant and coatings stable at high temperature
can be prepared using low-cost preceramic polymers. Commerically available
polyhydridomethylsiloxanes, [MeSiHO]x are firstly modified
by catalytic techniques and then mixed with ceramic and metallic powder
fillers to form suitable slurries or ``paints''. Alternatively, the polymers
used as clear coats. One-pot, and in-situ polymer modifications above to
conveniently control parameters such as surface wetting, curability, hardness,
and shelf stability, and hydrophobicity. Several unique polymers have been
produced using transition-metal catalyzed dehydrocoupling reaction including
polymers containing over 80 mol of the
monomeric units [MeSi(OH)(O)].
Thick coatings can be deposited (in the range of 50 to
100m per layer). The coatings are cured
at room temperature and remain stable at temperatures above 600C
when coated on aluminum or steel. Coatings cured at room temperature already
demonstrate excellent corrosion resistance properties. Thick coatings on
ceramics maintain their integrity and bonding to the substrates at temperatures
as high as 1500C. Formulation
strategies and the importance of polymer modifications will be discussed.
Characterization of coatings and performance evaluation in corrosive environments
will be presented.
4:30 PM DD7.10
HOST-GUEST SYSTEMS IN THE DEVELOPMENT OF ANTICORROSIVE
INTERACTIVE POLYMERIC FILMS. Luciana M. Estevao , Regina S. Nascimento,
Universidade Federal do Rio de Janeiro, Instituto de Quimica, Rio de Janeiro,
Techniques have been developed in which volatile corrosion
inhibitors (VCI) are incorporated into polymer films in order to reduce
the corrosion of metallic objects that occurs due to the condensation of
water vapor inside polymeric packaging. These inhibitors are transferred
to the metal surface by diffusion through the gas phase and are then either
adsorbed directly onto the metal or dissolved in surface moisture films.
Hence, the major parameters to be considered when using a VCI are their
volatility and, when processed in polymeric films, their thermal stability.
However, thermally stable VCIs such as dicyclohexylammonium phosphate and
p-nitrobenzoate, have relatively low volatility and may fail to meet VCI
standards. The most efficient and widely used VCI, dicyclohexylammonium
nitrite (DICHAN) degrades in the film processing temperature and is thus
inadequate for this purpose.
The aim of this project was to develop interactive films
making use of host-guest systems, where dicyclohexylammonium p-nitrobenzoate
and phosphate were adsorbed on NaY zeolite and diatomaceous earth, thus
controlling the volatility of the inhibitors. The changes in volatility
of the various systems were determined by TG/DTG analysis, and their protective
properties, by accelerated corrosion testing, making use of carbon steel
test coupons. The most promissing VCI/Inorganic support systems were processed
with a LDPE/EVA mixture to produce anticorrosive films, which were thereafter
submitted to further corrosion testing.
The VCI systems produced presented good thermal stability
and the results showed that the adsorption of the VCIs on the supports
shifted the DTG peaks to lower temperatures, indicating an increase in
volatility, which in turn led to a greater corrosion protection in phosphate
systems. It was thus observed that polyolefin interactive films of dicyclohexylammonium
phosphate guest molecules on porous inorganic support hosts gave rise to
an efficient means of corrosion protection for ferrous materials.
4:45 PM DD7.11 SYNTHESIS OF HYBRID ORGANIC-INORGANIC
SOL-GEL COATINGS FOR CORROSION RESISTANCE. Tammy Metroke , Edward Knobbe,
Oklahoma State Univ, Dept of Chemistry and the Environmental Inst, Stillwater,
OK; Robert Parkhill, Wright Laboratories, Materials Directorate, Wright
Patterson Airforce Base, Dayton, OH.
Sol-gel derived organically-modified silica thin films
are being investigated as potential replacement systems for chromate-based
conversion coatings for aluminum-skinned aircraft. Hybrid organic-inorganic
thin films, which may be tailored to have exceptional durability and adhesion,
while also providing a dense, flexible barrier, have been found to offer
protection from the permeation of water and corrosion initiating species.
Preparation, characterization, and corrosion resistance behavior of sol-gel
derived RSi(OCH3)3-TEOS thin films are presented.
SESSION DD8: POSTER SESSION:
SUPERLATTICES OF SEMICONDUCTOR QUANTUM SIZE PARTICLES
IN LAYERED ORGANIC ACIDS. Ronit Popovitz-Biro , Shouwu Guo, Volker Hensel,
Leslie Leiserowitz, Meir Lahav, The Weizmann Institute of Science, Department
of Materials and Interfaces, Rehovot, ISRAEL.
Wednesday Evening, April 7, 1999
Salon 7 (M)
The preparation and control of size and organization of
semiconductor nanoparticles has been a challenge in materials chemistry
research over the last years. This goal has been aproached from several
directions such as the use of reverse micelles1 or amphiphilic
polymers2 as media for their synthesis and arrangement. Previous
studies in our laboratory demonstrated that the crystalline lattice of ,-alkanedicarboxylate
metal salts can be used as confining templates for the synthesis of nanoparticles,
showing a dependance of particles size on chain length3 . Here
we report the preparation of lead sulfide and cadmium sulfide quantum particles
with a high degree of monodispersity arranged in periodic layers within
organic matrices. Superlattices of the particles have been generated in
crystals or thin films of long chain amphiphilic acids by topotactic gas-solid
reactions of the lead or cadmium salts with H2S gas. These metal
salts pack in layer structures and the metal ions are arranged in 2D layers
that are separated from one another by the distance defined by the dimensions
of the organic bilayer. X-ray powder diffraction (XRD) and transmission
electron microscopy (TEM) reveal that the ordered structure of the reactant
crystal or film has been retained in the organic-inorganic composite. The
approach is demonstrated by four examples of organic matrices: crystals
of alkanoic acids, self-organized thin films of -hydroxyalkyloxy-phenyl-propionic
acids spread at the air-solution interface4, crystals of alkyloxy-phenyl-propionic
acids and crystals of alkoxybenzoic acids.
(1) Motte, L.; Billoudet, F.; Lacaze, E.; Doin, J.; Pileni,
M.P., J.Phys.Chem.B 1997, 94, 3104.
(2) Osenar, P.; Braun, P. V., Stupp, S.I., Adv.Mater.
1996, 8, 1022.
(3) Guo, S.; Popovitz-Biro, R.; Weissbuch, I.; Cohen,
H.; Hodes, G.; Lahav, M., Adv.Mater. 1998, 10, 121.
(4) Guo, S.; Popovitz-Biro, R.; Arad, T.; Hodes, G.;
Leiserowitz, L.; Lahav, M., Adv.Mater. 1998, 10, 657.
PREPARATION OF NOVEL HOLLOW FIBER SILICA USING AN ORGANIC
GEL AS A TEMPLATE. Yoshiyuki Ono , JST, Chemotransfiguration Project, Kurume,
JAPAN; Junichi Hojo, Kyusyu Univ, Dept of chemistry and Biochemistry, Graduate
School of Engineering, Fukuoka, JAPAN; Seiji Shinkai, JST,Chemotransfiguration
Project, Kurume, JAPAN.
A novel hollow fiber silica was produced by the use of
the fibrous structures of an organic gel. The inner diameter ranged from
10 to 200 nm and the outer diameter ranged from 50 to 300 nm. An organic
gelator was dissolved in dichloromethane and mixed with the silicate solution
which consisted of TEOS/water/catalyst and the solvent that could be gelated
by the organic gelator: for example, TEOS/water/acetic acid and TEOS/water/benzylamine/1-butanol.
Subsequently, the resultant solution was evaporated in vacuo until the
dichloromethane was removed to give a turbid gel. The SEM images of the
product showed well grown fibrous structures. After calcination, it was
clearly seen by TEM images that these fibers have a tubular structure.
The preferable gelator to form hollow fiber silica is one which has cationic
charges: for example, a quaternary ammonium halide salt or a crown ether
including a metal cation. Cholesterol derivatives having azobenzene were
used as the organic gelator in this study. The diameter of hollow was comparable
with that of the organic gelator fibrils, so the gelator acted as a template.
Since the propagation species of silicate in the solution of acetic acid
or benzylamine are considered to be anionic, the electrostatic interactions
may be important for adsorption of silica onto the template fibers.
SELECTIVE METAL DEPOSITION VIA OMCVD ONTO SAMS. Roland
A. Fischer , Carl C. Winter, Ulrike M. Weckenmann, Ruhr-Universität
Bochum, Anorganische Chemie II, Bochum, GERMANY.
We demonstrate the selective deposition of ultrathin gold
layers by organometallic chemical vapor deposition (OMCVD) onto SH-terminated
self-assembled monolayers (SAMs) using the volatile gold precursor Me3PAuMe.
OMCVD has proven to be an ideal method for the deposition of metals on
SAMs which are extremely sensitive to elevated temperatures. Given a suitable
surface functionality the deposition can be carried out under very mild
conditions at high rates. The selectivity of this method relies on different
rates of the surface reaction on different surfaces. We have deposited
gold on patterned SAMs generated by microcontact printing with regions
terminated by CH3 or SH. This resulted in the formation of a
microstructured gold layer since deposition only occured on the reactive
SH-terminated areas. The deposition of gold and the formation of Au-S-bonds
on the surface has been shown by XPS (changes in the Au4f and S2p peak
intesities). AFM images reveal that the gold deposited on the surface of
the SAM forms clusters (20-40 nm) rather than a film of uniform thickness.
Further methods of investigation include RAIRS, SD-MS and STM.
POLYSILSESQUIOXANES DERIVED FROM METHACRYLOXYLPROPYLTRIMETHOXYSILANE:
COPOLYMERIZATION REACTION WITH STYRENE. Patricia Eisenberg , Juan Carlos
Lucas, INDEMAT-UNSAM-CITIP-Inst. Nac. de Tecnologia Industrial, Bs. As.,
ARGENTINA; Roberto J. J. Williams, INTEMA-CONICET, Univ. Nacional de Mar
del Plata, Bs. As., ARGENTINA.
Polysilsesquioxanes (SSQO) are the reaction products of
the hydrolytic condensation of trifunctional organosilicon monomers (RSiX3).
The term polysilsesquioxane is used to describe both oligomeric polyhedra
that are fully condensed structures ([RSiO1.5]n,
with n = even integer number), and open structures that are incompletely
condensed reaction products ([RSiO1.5-x(OH)2x-n]n)
(1). If R is a polymerizable functional group, a polymer network derived
from the SSQO may be obtained. In this presentation we discuss the synthesis
and characterization of the particular hybrid material derived from the
hydrolytic condensation of methacryloxypropyl trimethoxysilane, followed
by copolymerization with styrene.The hydrolytic condensation was performed
in bulk, using formic acid 98-100 (2),
at 50C, 2 days. The distribution
of reaction products was followed by SEC. After an initial period of several
hours, two main peaks were observed. The first one was assigned to SSQO
with n = 8-12 while the second one was ascribed to SSQO with n = 16 .The
organic polymer network was obtained by a free-radical copolymerization
of R groups with styrene (10-90
wt). The copolymerization reaction was followed by DSC. For formulations
containing 60 wt of styrene or more,
the reaction heat was constant and equal to the one reported for the styrene
homopolymerization .Formulations containing lower styrene contents exhibited
a decrease in the overall reaction heat. Thermal and mechanical properties
of the hybrid materials were determined as a function of the styrene content.
The Tg was determined by TMA. Tg was equal to 100C
for pure polystyrene and increased to about 140C
for the formulation with 60 wt styrene.
Samples with lower styrene contents did not exhibit a Tg by TMA up to 300C.
Thermal gravimetric analysis showed that the decomposition temperature
increased from 418C (80 wt
styrene) to 431C (10 wt
styrene). The ceramic yield to SiO2 (oxygen at 900C)
(3) was the theoretical one within experimental error. A significant increase
in Barcol hardness was observed (72 for 10 wt
styrene; 44 for 80 wt styrene). Ref.
1. Provatas, A.; Matisons, J.G.; Trip, 5, 327, 1997.
2. Sharp, K.; J.Sol.-Gel Sci. Techn.; 2, 35, 1994. 3.
Sellinger,A.; Laine,R.M.; Macromolecules,29, 2327, 1996.
PREPARATION OF SPHERICAL HYDROUS SILICA OXIDE PARTICLE
UNDER ACIDIC CONDITION VIA SOL-GEL PROCESSING. Yang Wu , Satsuki Kitajima,
Mika Ohsawa, Mamoru Aizawa, Kansai Research Institute (KRI), Kyoto, JAPAN.
It is well known to prepare spehrical particles via sol-gel
processing employing such famous process as Stoeber Process, and so on.
Usually, particles are formed under basic condition, however, we have found
that spherical hydorus oxide particles could be formed under acidic condition.
The reaction mechanism was supposed to be a kind of suspension polymerization.
Those particle diameter ranged from 1 micrometer to 1000micrometer. Particle's
size was controlled by adding seed particles, other metal species like
Ti, Zr and so on. During the particle formation process, we could easily
introduce not only functional molecules but also fine particles into spherical
particles. Those particles were basically optically clear and showed some
A SILICON AND DEUTERIUM NMR INVESTIGATION OF MOLECULAR
TEMPLATING IN AMORPHOUS SILICAS. Roger A. Assink 1, Carol A.
Click2, Todd M. Alam1, C. Jeffrey Brinker1,3
and Sujit J. Naik3, 1Sandia National Laboratories,
Albuquerque, NM; 2University of Missouri, Rolla, MO and 3University
of New Mexico, Albuquerque, NM.
The precise pore sizes defined by crystalline zeolite
lattices have led to intensive research on zeolite membranes. Unfortunately
zeolites have proven to be extremely difficult to prepare in a defect-free
thin film form needed for membrane flux and selectivity. We introduce tetrapropylammonium
TPA (a structure directing agent for zeolite ZSM-5) into a silica sol and
exploit the development of high solvation stresses to create templated
amorphous silicas with pore apertures comparable in size to those of ZSM-5.
Silicon and deuterium NMR experiments were performed to evaluate the efficacy
of our templating approach. The 29Si NMR spectrum of the silica matrix
was observed by an intermolecular cross-polarization experiment involving
the 1H nuclei of TPA and the 29Si nuclei in the silica matrix. The efficiency
of the cross-polarization interaction was used to investigate the degree
to which the matrix formed a tight cage surrounding the template molecule.
Normally prepared xerogel materials exhibited only weak interactions between
the two sets of nuclei. Drying under reduced pressure where solvation stresses
are maximized resulted in significantly increased interactions. Analogous
materials were prepared using fully deuterated TPA. The 2H NMR wideline
spectra consisted of a partially narrowed resonance, corresponding to template
molecules which were undergoing restricted rotational motion, and an isotropically
narrowed resonance, corresponding to molecules which were undergoing rapid
rotational motion. The number of freely rotating template molecules decreased
for specimens dried under reduced pressure, consistent with improved templating
of amorphous silica by TPA.
Sandia is a multiprogram laboratory operated by Sandia
Corporation, a Lockheed Martin Company, for the United States Department
of Energy under Contract DE-AC04-94AL85000.
THERMOSETTING MACHANISM STUDY OF ORGANOSILICON POLYMER
CONTAINING CARBORANE BY SOLID-STATE NMR SPECTROSCOPY. Hideaki Kimura ,
Kouichi Okita, Japan Chemical Innovation Institute, Advanced Polymer Lab,
Tsukuba, JAPAN; Motokuni Ichitani, Mitsuharu Yonezawa, Toshiya Sugimoto,
Sekisui Chemical Ltd, Advanced Polymer Lab, Osaka, JAPAN.
The thermosetting mechanism of organosilicon polymer containing
carborane has been studied utilizing the 13C and 29Si
solid-state NMR method. The polymer having C-C triple bond in the main
chain and CH=CH2, Si-H bonds, and carborane in the bulky side
chain, shows a very highly thermal stability by curing at 350C.
From these results, it was found that the CH=CH2, Si-H bonds
in the side chain completely vanished up to 250C,
whereas all of C-C triple bonds in the main chain were not involed in cross-linking
reaction even at 350C. Consequently,
it is thought that the organosilicon polymer was flexible even after cross-linking.
ULTRATHIN FILMS OF DENDRIMER-METAL NANOCOMPOSITES. Lajos
Balogh , University of Michigan Center For Biologic Nanotechnology, Ann
Arbor, MI; Srinivas Uppuluri, Jing Li and Donald A. Tomalia, Michigan Molecular
Institute, Midland, MI; Gary. L. Hagnauer, AMSRL-WM-MA, US Army Research
Laboratory, APG, MD.
Dendrimer based nanocomposites (DNCs) are recently discovered
hybrid materials displaying unique physical and chemical properties as
a consequence of the atomic/molecular level dispersion of inorganic guest
domains within a dendritic organic host. Self-assembled monolayers (SAMs)
of molecules are capable of molecular recognition and have many potential
applications. Layer-by-layer electrostatic deposition is a facile way of
creating orderly deposited multilayer films. In this work poly(amido-amine)
dendrimers were used to prepare multilayers of zero valent metals on different
substrates by using Cu(0)-PAMAM, Ag(0)-PAMAM and Au(0)-PAMAM dendrimer
nanocomposites. Gold and silver containing intradendrimer and interdendrimer
multilayer alloys of Ag(0)-PAMAM, Au(0)-PAMAM and (Au(0)-Ag(0))-PAMAM nanocomposites
were also fabricated. By employing DNCs, not only the fabrication of multilayers
proved to be quick and efficient but the composition and structure of multilayers
can be varied at will. Advantages of using dendrimer nanocomposites will
be discussed in the light of dynamics of multilayer formation. Also, uncommon,
architecture-dependent properties of the metal multilayers will be compared.
DIALKYLENECARBONATE-BRIDGED POLYSILSESQUIOXANES HYBRID
ORGANIC SOL-GELS WITH A THERMALLY LABILE BRIDGING GROUP. Douglas A. Loy
, James V. Beach, Brigitta M. Baugher, Roger A. Assink, Encapsulation and
Foams Department, Sandia National Laboratories, Albuquerque, NM; Kenneth
J. Shea, Joseph Tran, Department of Chemistry, University of California,
Irvine, CA; James H. Small, Polymers and Coatings Group, Los Alamos National
Laboratory, Los Alamos, NM.
Gelation of polysilsesquioxanes is limited to those functionalized
with a relatively limited group of organic substituents. By capitalizing
on the greater propensity of bridged polysilsesquioxanes to form gels,
it is possible build polymeric architectures whose bridging organic functionality
contain a masked chemical functionality that can be thermally released
after the desired gel structure has been obtained. Dialkyl carbonates can
serve as masking groups for either an olefin and an alcohol or two alcohols
depending on how the carbonate is decarboxylated. In this work we prepared
dialkylenecarbonate-bridged polysilsesquioxane gels by the sol-gel polymerization
of bis(triethoxysilylpropyl)carbonate (1) and bis(triethoxy- silylisobutyl)carbonate
(2). Thermal treatment of the resulting non-porous xerogels and aerogels
at 300 °C resulted in the quantitative decarboxylation of the dialkylenecarbonate
bridging groups to give new hydroxyalkyl and olefinic substituted polysilsesquioxane
monolithic xerogels and aerogels that can not be directly prepared through
direct sol-gel polymerization of alkoxysilane precursors.
METAL PHOSPHONATE LANGMUIR-BLODGETT FILMS CONTAINING
FUNCTIONAL ORGANIC GROUPS. Melissa A. Petruska and Daniel R. Talham, Univ
of Florida, Dept of Chemistry, Gainesville, FL.
The Langmuir-Blodgett (LB) deposition procedure allows
for the fabrication of thin films by arranging amphiphilic molecules at
an air-water interface before transferring them onto a solid support. By
modeling LB films after organic/inorganic layered solids, the lattice energy
and other physical phenomena associated with inorganic extended solids
can be incorporated into the thin films. For example, octadecylphosphonic
acid films as divalent, trivalent, or tetravalent metal salts form bilayer
LB film structures where the metal phosphonate networks have the same in-plane
binding as the analogous layered solid-state metal alkylphosphonates. This
metal/phosphonate network also provides the opportunity to incorporate
functionalized organic groups into the LB films, thereby creating a material
where both the inorganic and the organic components add function to the
LB assembly. Working toward such systems, we have recently introduced larger
organic moieties into LB films formed by the metal phosphonate approach.
Studies of an azobenzene-derivatized phosphonic acid have probed the limitations
encountered when forming these metal phosphonate films, particularly when
the preferred organic packing is incommensurate with the inorganic lattice.
Phosphonic acids containing tetrathiafulvalene groups have also been synthesized,
and metal phosphonate films of these derivatives with divalent and trivalent
metal ions have been prepared and characterized using FTIR, optical spectroscopy,
and conductivity measurements.
FORMATION AND HYDROLYTIC STABILITY OF OXYGEN BRIDGED
HETEROMETAL BONDS (Si-O-Ti, Si-O-Zr, Si-O-Ta) IN SOL-GEL MATERIALS. Manfred
Nacken , Dagobert Hoebbel, Helmut Schmidt, Institut fuer Neue Materialien,
Glycidoxypropyltrimethoxysilane (GPTS) and metal alkoxides
are frequently used in preparation of heterometal hybrid polymers, which
find application in electronic and optical industry e.g. as hard coatings
of organic polymers and contact lens materials. Such materials require
a high homogeneity of the structural unit on molecular level, which is
supported by the formation of oxygen bridged heterometal bonds and their
hydrolytic stability. By means of 29Si and 17O NMR
the formation of heterometal bonds like Si-O-Ti, Si-O-Zr, Si-O-Ta could
be identified in the GPTS-hydrolysates with Ti(OEt)4, Ti(OEt)3AcAc,
Ta(OEt)5 or Ta(OEt)4AcAc (AcAc = acetylacetone ligand).
Signals of heterometal bonds can be detected in 17O NMR spectra
in the region of 170 to 350 ppm. They are characterised in 29Si
NMR spectra by defined chemical shifts to low (Si-O-Ta) and high magnetic
fields (Si-O-Ti, Si-O-Zr). The use of complexed metal alkoxides with AcAc
as ligands leads to well resolved 29Si NMR spectra, which make
the distinction between homo- and heterocondensed species easier. The addition
of water (0.5-2 H2O/alkoxy group) to heterometal bond containing
systems leads to a degradation of Si-O-M bonds (M= Ti, Zr, Ta) in favour
of more homocondensed species, which can lower the homogeneity of such
hybrid materials on a molecular level.
ATOMIC FORCE MICROSCOPY STUDY OF THE REORGANIZATION OF
LANGMUIR-BLODGETT FILMS. Dawn Y. Takamoto , Evgeny Ter-Ovanesyan and Joseph
A. Zasadzinski, University of California, Santa Barbara, Dept of Chemical
Engineering, Santa Barbara, CA.
The practical applications of Langmuir-Blodgett (LB) monolayers
and multilayers are limited by a spontaneous reorganization in aqueous
solution. The reorganization of cadmium fatty acid salt LB films was studied
by equilibrating under aqueous subphase for various times, and then imaging
with the atomic force microscope (AFM) in air. We have found that constant
thickness films deposited on both hydrophilic and hydrophobic substrates
(mica and silicon) are unstable to bilayer step defects.
Multilayer fatty acid salt LB films are isostructural
with centrosymmetric bulk soap crystals. The LB technique deposits asymmetric
molecules onto the substrate surface which are inherently unstable, and
the molecules undergo a conformational transition resulting in defective
layers. To elucidate the mechanism for the reorganization, we deposited
LB films with layers of varying chain lengths. From measurements of the
heights of the bilayer step islands and holes formed, we were able to determine
how the molecules were rearranging between layers. This gave us an indication
that the reorganization proceeds by a bulk folding of the layers, which
is consistent with the island morphology.
Cadmium LB films deposited at high pH (approximately
8.5) have a different stoichiometry of one cadmium cation for every fatty
acid. These molecules do not undergo a conformational transition, and this
leads to a significantly reduced rate of reorganization for these films.
This result shows that if we can create LB films that maintain their deposited
structure throughout the layers, then we can eliminate the instability
of fatty acid salt films.
HYDROTHERMAL SYNTHESES AND STRUCTURAL CHARACTERIZATIONS
OF A THREE-DIMENSIONAL MICROPOROUS GALLIUM MANGANESE PHOSPHATE (C4N2H12)2Ga5(H2O)Mn2(PO4)8
AND A LAYERED GALLIUM PHOSPHATE (C6N2H16)Ga2(C6N2H14)(PO4)2(HPO4).
Kuei-Fang Hsu , Chia-Heir Lin, Sui-Lein Wang, Dept of Chemistry, Natl Tsing
Hua University, Hsinchu, TAIWAN.
Hydrothermal syntheses of the A/Ga/P/O (A = piperazine,
and 1,2-diaminocyclohexane) system has been investigated. Two novel gallium
phosphate phases, (C6N2H16)Ga2(C6N2H14)(PO4)2(HPO4)
(1) and (C4N2H12)2Ga5(H2O)Mn2(PO4)8
(2), have been prepared under mild T/P conditions. Phase 1 adopts a layer
structure in which protonated amine cations are between layers. The anionic
layer is built up of octahedron of GaO4N2 and tetrahedra
of GaO4, PO4 and HPO4, respectively. Interestingly,
the organic amine molecules plays two roles in the formation of phase 1:
one half of 1,2-diaminocyclohexane molecules are coordinated to Ga atoms
as bidentate ligands and the other half are protonated as templates to
the structure. Being the first mixed manganese (II, III) gallium phosphate,
phase 2 was obtained using piperazine as a structure-directing reagent.
It adopts a 3D open framework structure in which three kinds of polyhedra
coexist: octahedron of GaO6, bipyramid of GaO5, and
tetrahedra of MnO4, and PO4. These polyhedra are
interconnected via a corner-sharing manner to give a zeolitic framework
in which large and straight channels are formed inside the structure. The
piperazinium cations are residing in the tunnel at two crystallographic
sites such that they are staggering along the channel directions. In this
paper, hydrothermal syntheses, crystal structures, and thermal properties
of the title compounds will be presented in detail.
SESSION DD9: POSTER SESSION:
FASH ION CONDUCTING SILVER-SILICATE XEROGELS: SYNTHESIS
AND STRUCTURAL INVESTIGATIONS. N. Satyanarayana, A. Keith King and B. Rambabu
, Southern University and A&M College, Surface Science, Spectroscopy
and Solid State Ionics Laboratory, Department of Physics, Baton Rouge,
Wednesday Evening, April 7, 1999
Salon 7 (M)
Silver-silicate based fast ion conducting (FIC) compounds
have become increasingly popular in the field of solid state ionic device
technologies due to their structural stability and increased ionic conductivity.
Among the known preparation techniques, recently, the sol-gel synthesis
technology has become a viable and alternate technique for the preparation
of toiler made fast ion conducting materials for custom designed ionic
devices. In this work, we have made an attempt to synthesize fast ion conducting
binary oxide xerogels [(XAg2O+(1-X)SiO2) (SS); X=0.1
to 0.9 in steps of 0.1]. Structural properties were investigated by using
XRD, IR, DSC, SEM, EDS, WDS and impedance spectroscopy techniques.
Analar grade chemicals of AgNO3, HNO3,
Si(C2H5O), tetraethylorthosilicates (TEOS), C2H5OH,
supplied by Aldrich Co., USA, and double distilled water were taken and
mixed at different stages. The sol-gels were prepared by mixing the following
A and B solutions. Solution A was prepared by dissolving the TEOS in C2H50H
and the required amount of H20 was added to the solution (TEOS
+C2H5OH) on continuous stirring. Solution B, prepared
by dissolving AgNO3 in the required quantity of water (H2O),
was added to the solution A under continuous stirring. The sol was then
cast in a beaker and allowed to form a gel at 40C.
Clear transparent gels were obtained within 72 hours. The gels were then
allowed to dry at 40C, in order
to obtain the xerogels and were grounded well and made into fine powders.
All the compositions of the SS xerogels were characterized to determine
the nature, structure and electrical conductivity of each composition of
the SS system. Detailed results on SS system will be presented and discussed.
Acknowledgement: B.Rambabu acknowledges the RCS program
at LLNL and US DOE-Office of Basic Energy Sciences for supporting this
work through a subcontract and a grant.
SYSTEM FOR PRIMARY BATTERIES: SOL-GEL SYNTHESIS AND CHARACTERIZATION.
N. Satyanarayana 1 and B. Rambabu, Southern Univeristy and A&M
College, Surface Science, Spectroscopy and Solid State Ionics Laboratory,
Department of Physics, Baton Rouge, LA; P. Muralidharan, Pondicherry University,
Department of Chemistry, Pondicherry, INDIA; R. Patcheammalle and M. Venkateswarlu,
1Pondicherry University, Department of Physics, Pondicherry,
Sol-gel technology has gained interest in the field of
superionic conducting materials to synthesize different types of glasses,
polycrystalline, ceramic materials in the forrn of monoliths, fine powders,
thin films, etc. New superionic conducting materials synthesized through
sol-gel technique have received more importance due to their applications
of various electrochemical devices. Of which, lithium based solid electrolytes
are promising materials for utilization in the solid state batteries. The
aim of this work is to synthesize lithiumborophososilicate (LBPS) system
by sol-gel process, characterization and study their impedance & battery
discharge characteristics. Sol-gels are prepared by mixing analar grade
chemicals using the following formula 20Li2O-80%[0.2P_2O_5+0.8(xB_2O_3+(1-x)SiO_2)],
X=0.0 to 1.0 in steps of 0.1. For one of the compositions,
0.1N nitric acid as catalyst, solution A contains tetraethylorthosilicate
(X; Br and I, abbreviated as PhE-PbX4 hereafter) were fabricated
on glass substrates by the spin-coating method. The prepared films showed
stable exciton absorption with narrow bandwidth and free-exciton emission
even at room temperature. However, the films were not stable against the
UV-light irradiation. The PhE-PbX4 films were readily oxidized
by that UV-light irradiation in air. In vacuum, the PhE-Pbl4
films changed to -phenethylamine
intercalated Pbl2 due to the elimination of halogen spices.
On the contrary, no degradation was observed for the PhE-PbBr4 films. These
results suggested that the light irradiation-induced photochemical reaction
was one of the possible reasons for the degradation. To suppress the oxidation
and halogen elimination induced by the photochemical reaction, nanocrystalline
PhE-PbX4 doped PMMA films were also fabricated by the spin-coating
and subsequent annealing. Although the nanocrystals dispersed in PMMA gradually
decomposed by the UV illumination, marked improvement of the photostability
was achieved. In conclusion, the photostability can be improved by doping
the nanocrystalline PhE-PbX4 into a PMMA matrix.
OPTICAL WAVEGUIDE OF INORGANIC/ORGANIC HYBRIDS CONTAINING
VARIOUS INORGANIC COMPONENTS DERIVED FROM METAL ALKOXIDES. Noriko Yamada
, Ikuko Yoshinaga and Shingo Katayama, Nippon Steel Corporation, Advanced
Technology Research Laboratories, Kawasaki, JAPAN.
Inorganic/organic hybrid films containing various inorganic
components are expected as a host material to incorporate organic photoactive
molecules because of the controllability of refractive indices and heat-resistance
derived from inorganic components together with the flexibility derived
form organic components. Planar optical waveguides of inorganic/organic
hybrid films containing various inorganic components were synthesized from
diethoxydimethylsilane and metal alkoxides modified with ethyl acetoacetate.
Ti, Zr and Ta alkoxides were used as a precursor of the inorganic components.
Inorganic/organic hybrid films were prepared on a quartz glass substrate
by spin-coating, followed by drying and heat-treating. The thickness of
the hybrid films was 0.60-0.78 m.
The hybrid films containing inorganic components derived from Ti, Zr and
Ta alkoxides have 1.65, 1.55 and 1.64 in refractive index of
= 633 nm, respectively. The hybrid films showed relatively low values of
the optical losses and also small in-plane scattering as a planar waveguide,
although they were not prepared in a clean room. The optical loss values
of the hybrid films containing inorganic components derived from Ti, Zr
and Ta alkoxides were 6.19, 5.16 and 12.08 dB/cm, respectively.
Research supported lay NEDO, under the Synergy Ceramics
Project of the ISTF program promoted by AIST, MITI, Japan.
PHOTOELECTRIC PROPERTIES OF MATERIAL OF N,N'-BIS(4'-AMINOPHENYL)
-1,4-QUINONENEDIIMINE DOPED WITH HETEROPOLY ACID. Gong Jian, Yang Ji-Hua,
Gui Xiu-Jun, Su Zhong-Min, Qu Lun-Yu , Department of Chemistry, Northeast
Normal University, Changchun, CHINA.
Polyaniline is a kind of important photoelectric material
because of its potential application in fields such as conductivity, LED
and so on. Recently, the aniline oligomer is obtaining much more attention
due to the structure and size advantages. In this paper, we have synthesized
aniline oligomer with different doping heteropoly acid (H4SiW12O40)
and investigated the effect of doping on their UV-Vis absorption spectra
and fluorescence properties. The doping and dedoping process of the aniline
oligomer was investigated via UV-Vis spectra, pH=5.5 was turning point
of doped and dedoping.The band at 572nm disappeared and the bands at 268nm,
412nm, and 771nm appeared after the aniline oligomer was doped. In a certain
range, the doping is favorable for a increase of intensity of the fluorescence
emission band at 860nm, although the corresponding characteristic absorption
band (572nm) is weakened. And at the same time, the fluorescence emission
in Vis region (ca. 640nm) is observed, which is caused by the new electronic
transition band induced by the doping effect of heteropoly acid. All of
these suggest that the aniline oligomer doped with heteropoly acid as a
new type light emitting material have an attractive prospect. LED of the
new material is being exploited.
HIGHLY ELECTRICAL CONDUCTIVITY OF HYBRID LANGMUIR-BLODGETT
FILMS OF TRANSITION METAL DICHALCOGENIDE AND AMPHIPHILIC CATIONS. Hiroaki
Tachibana , Joint Research Center for Atom Technology (JRCAT) and National
Institute of Materials and Chemical Research, Tsukuba, JAPAN; Yasushi Yamanaka,
Mutsuyoshi Matsumoto, National Institute of Materials and Chemical Research;
Reiji Kumai, JRCAT, Tsukuba, JAPAN; Yoshinori Tokura, JRCAT and University
of Tokyo, Tokyo, JAPAN.
Layered transition metal dichalcogenide MX2,
where M is a transition metal and X is S or Se, have been extensively investigated
for their interesting electrical properties such as superconductivity and
their application as cathode materials for rechargeable high-energy-density
lithium batteries. A variety of organic compounds such as polymers can
be intercalated into the layered structures. The organic-inorganic hybrid
materials can show hybrid physical and chemical properties. In this paper,
we present the formation of the hybrid alternate layered Langmuir-Blodgett
(LB) films of an amphiphilic ammonium cation and a transition metal dichalcogenide.
The hybrid layered LB films were prepared as follows. Single molecular
layers of MX2 dispersed in water were prepared by intercalation
of Li into MoS2, followed by exfoliation in water. A convenient
method using n-butyllithium (n-BuLi) in hexane was used as the intercalation
agent. Chloroform solution of the amphiphilic cations was spread onto suspension
of single layers of MX2. The hybrid monolayer was transferred
using the LB method onto solid substrates. The electrical conductivity
of the hybrid LB films of MoS2 and amphiphilic cations was above
100 Scm-1 at room temperature and was very stable. The condcutivity
depended on the concentration of MoS2 dispersed in water, the
amphiphilic cation, and the transition metal dichalcogenide. The optical
properties of the hybrid layered LB films will also be described.
NANOSCOPICALLY DESIGNED HYBRID DUMBBELL POLYMERS FOR
HIGH PERFORMANCE APPLICATIONS. Derek Lincoln , Richard Vaia, Materials
and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson
AFB, OH; Matthew Marrocco, Aaron Adler, Maxdem, Inc., San Dimas, CA; Traui
Walker, Timothy Haddad, Propulsion Directorate, Air Force Research Laboratory,
Edwards AFB, CA.
Recent advances in the synthesis of high molecular weight
polyparaphenylenes have led to the production of a new class of rigid-rod
polymers with excellent isotropic mechanical properties and processability.
Such polymers have been shown to possess an isotropic tensile and flexural
modulus of nearly three times that of common engineering polymers and retain
a high storage modulus well above Tg. These polymers also display good
melt processability and good solubility in a wide variety of organic solvents
making them promising for use in a wide range of engineering applications.
Likewise, recent investigations of polyhedral oligomeric silsesquioxane
(POSS) macromers have also shown polymeric materials displaying enhanced
thermal stability. POSS macromers possess inorganic silica-like cores with
seven inert and one reactive organic group. Polymerization at the single
reactive site leads to the formation of a linear polymer with nanosized
inorganic pendant groups. Thermolysis studies on such polymers have shown
that they undergo a polymer-ceramic conversion process forming SiOxCy chars
rather than burning. The work presented here describes the behavior of
substituted polyparaphenylenes with various POSS macromers (chlorophenyl
or chlorobenzyl POSS at 5 and 10wt%) incorporated as end-groups. This work
includes studies of these polymers using dynamic mechanical analysis (DMA),
differential scanning calorimetry (DSC), thermogravimetric analysis (TGA),
x-ray scattering techniques, and transmission electron microscopy (TEM)
with the end goal of understanding the thermolysis and ablative properties.
OPTICAL CHARACTERISTICS OF SILICA-PEO HYBRID THIN FILMS.
Oun-Ho Park , Young-Joo Eo, Yoon-Ki Choi and Byeong-Soo Bae, KAIST, Dept
of Materials Science and Engineering, Lab. Optical Materials and Coating,
Silica-poly(ethylene oxide)(PEO) hybrid materials which
have both silica network and polymer network are synthesized from hydrolysis,
condensation and polymerization of -glycidoxypropyltri-
methoxysilane(GPTS). Polymerization of the epoxy groups to poly(ethylene
oxide) units is achieved by using 1-methylimidazol as a thermal curing
agent or mixed triarylsulfonium hexafluorophosphate salt as a UV curing
agent. The structural change of the hybrid solution is investigated by
using NMR spectroscopy. The microstructure of silica-PEO hybrid film is
changed according to the degree of polymerization controlled by the thermal
or UV curing conditions. The epoxide polymerization is confirmed by using
FT-IR and differntial scanning calorimetry(DSC). The hybrid material is
densified due to the epoxide polymerization by thermal or UV curing as
well as silica condensation. The optical properties such as refractive
index, extinction coefficient and optical transmittance of the silica-PEO
hybrid films are measured as functions of curing conditions. The variation
of the optical characteristics depending on the epoxide polymerization
will be discussed.
PHOTOELECTROCHEMICAL PROPERTIES OF POLYANILINE-CdS FILMS.
D. Gonccalves , Inst Física de São Carlos, Univ São
Paulo, São Carlos, SP, BRAZIL; L.O.S. Bulhões, Dept de Química,
Univ Federal de São Carlos, São Carlos, SP, BRAZIL.
CdS particles with sizes ranging from 50 to 100 nm were
synthesized by chemical precipitation of Cd(NO3)2
and Na2S in aqueous solution. PANI-CdS films were obtained on
platinum electrodes by cyclic voltammetry or electrolysis of aniline in
the presence of a CdS suspension. According to the observed by scanning
electronic microscopy, PANI-CdS films showed a porous structure with CdS
nanoparticles incorporated in the whole surface of the film. Electrochemical
impedance and photoelectrochemical measurements were made on PANI and PANI-CdS
films since both results allow determining their semiconductor properties.
For a typical semiconductor, the capacitance of the space-charge layer
(CSC) obeys the Mott-Schottky equation. Mott-Schottky
plots were made on PANI and PANI-CdS films in the region of the first redox
process of PANI. In the range of frequencies from 1 Hz to 50 kHz, the contributions
to CSC are electronics and mass transport effects are
not significant. CSC values for both films presented
little variations (in order of 1021 cm-3) with film
thickness and preparation method (cyclic voltammetry or electrolysis).
PANI and PANI-CdS were also studied in dark and under UV and visible light.
A time of 20s was obtained by photocurrent measurements being associated
with the occurrence of photothermal processes. In the presence of Na2C2O4
(an efficient, irreversible hole scavenger), this value decreased to 2-3s.
Higher photocurrent values were obtained for PANI-CdS films as a result
from photoexcitation of the polymer and/or colloidal CdS particles, which
do not (i) represent a new phase and (ii) favor a charge movement discontinuity.
The quantum efficiency of the photocurrent at more positive potentials
is about 6x10-4, a typically low value since (i) recombination
is the dominant process in the oxidized polymer or (ii) a highly efficient
process occurs for a small number of photons absorbed by the CdS nanoparticles.
SURFACE MODIFICATION OF POLYMER WITH GRAFTING AND COATING
OF SILANE HYBRIDS AND THEIR BIOACTIVITY. Masaaki Kubo , Kanji Tsuru, Satoshi
Hayakawa, Akiyoshi Osaka, Okayama Univ, Faculty of Engineering, Biomaterials
Lab, Okayama, JAPAN; Chikara Ohtsuki, Nara Institute Science and Technology,
Graduate School of Materials Science, Nara, JAPAN; Seisuke Takashima, Okayama
Univ, Co-Operative Reserch Center, Okayama, JAPAN.
Materials involving both silanol groups and Ca2+ ions
show ability of bonding to living tissue or bioactivity: bone-like apatite
is deposited on such materials when soaked in a body environment, and the
bone cells are firmly attached to the apatite layer. One can provide polymers
with the bioactivity by modifying the surface with those chemical species.
In the present study, a silane coupling agent was grafted to such organic
polymers as HDPE, polyamide or PVC. Ormosil-type film was then coated via
sol-gel processes on the grafted surface. Bioactivity was examined by using
a simulated body fluid. Bonding strength between the substrate and the
coating film will be discussed.
ELECTRONIC PROPERTIES OF THE MODEL ORGANO- METALLIC POLYMER
[M-C(C(N)]n (M = Cu(I), Ag(I), Au(I). Su Zhong-Min , Wang Rong-Shun, Che
Chi-Ming, Institute of Functional Material Chemistry, Department of Chemistry,
Northeast Normal University, Changchun, CHINA.
The organometallic complexes of transition metal M = Cu(I),
Ag(I), Au(I) with d10 electronic configuration have abundant optical, electronic
and magnetic properties, so it is possible to prepare the high functional
organometallic polymer materials by coordinating (-conjugated organic molecules
with d10 metals. According to the experimental structures, the model polymers
[M-C(C(N)]n are built up and calculated by quantum chemistry methods. It
is indicated from theoretical analysis that the organometallic polymer
would have comparable conductivity when the interaction exists between
metals and pi electrons of different chains.
POROSITY IN POLYSILSESQUIOXANE XEROGELS. Duane A. Schneider
, Brigitta M. Baugher, Douglas A. Loy, Encapsulation and Foams Department,
Sandia National Laboratories, Albuquerque, NM.
Polymerization of organotrialkoxysilanes is a convenient
method for introducing organic functionality into hybrid organic-inorganic
materials. However, not much is known about the effects of the organic
substituent on the porosity of the resulting xerogels. In this study, we
prepared a series of polysilsesquioxane xerogels from organotrialkoxysilanes
(RSi(OR')3) with different organic groups (R = H, Me, Et, dodecyl,
hexadecyl, octadecyl, vinyl, chloromethyl, cyanoethyl). Polymerizations
of the monomers were carried out under a variety of conditions, varying
monomer concentration, type of catalyst, and alkoxide substituent. The
effect of the organic substituent on the sol-gel process was often dramatic.
In many cases, gels were formed only at very high monomer concentration
and/or with only one type of catalyst. All of the gels were processed as
xerogels and characterized by scanning electron microscopy and nitrogen
sorption porosimetry to evaluate their pore structure.
NEW MATERIALS WITH IMPROVED PROPERTIES FROM POLYMER-CERAMIC
NANOCOMPOSITES. Frank-Dieter Kuchta , Dutch Polymer Institute, Eindhoven,
THE NETHERLANDS; Hartmut R. Fischer, Lawrence F. Batenburg, TNO-TPD Materials
Research & Technology, Eindhoven, THE NETHERLANDS.
The aim of the present study is to exhibit the potentials
of new materials based on polymer-ceramics and to understand the action
of nano-scaled inorganic particles within a polymer matrix with respect
to the ultimate material properties. From the fundamental work of researchers
at Toyota Central Research and Development Laboratories on nanocomposites
based on polyamide-6 and layered silicates (i. e. clay minerals) it became
apparent, that due to the high aspect ratios of inorganic nano-scaled particles
materials are obtained that show improved mechanical, thermal and barrier
properties without a significant loss of optical transparence, toughness
or impact strength. Within the present investigation the effect of an external
confinement introduced by highly anisotropic silicate layers of organically
modified clay minerals on nanocomposite properties and crystal structure
has been studied on polyamide-6, polyamide-11, polyethylene and polypropylene.
The composites were prepared both by in situ polycondensation and by reactive
blending via melt extrusion. All nanocomposites exhibit a homogeneous distribution
of individual silicate layers within the host polymer at low clay content.
In polyamide-11 crystallization the lamellar thickening growth is reduced
as an effect of external constrained of the silicate layers in the host
polymer. As a result, the nanocomposites based on polyamide-11 show an
enhanced thermal stability and tensile modulus. Furthermore results on
thermal and mechanical properties of polyethylene and polypropylene nanocomposites
are presented where block-copolymers have been used to achieve homogeneous
intercalation of layered silicates within the host matrix. A new application
of polymer-clay nanocomposites applied in the pigment field will be pointed
SESSION DD10: BIOMEDICAL APPLICATIONS OF
8:30 AM *DD10.1
MICROPATTERNED POLYMER SUBSTRATES FOR CONTROLLING NERVE
CELL GROWTH. Kathryn Uhrich , Kristine Schmalenberg, Rutgers University,
Department of Chemistry, Helen Buettner, Rutgers University, Department
of Chemical & Biochemical Engineering, Piscataway, NJ.
Chair: Lorraine F. Francis
Thursday Morning, April 8, 1999
Salon 11/12 (M)
Microlithography is a technique that has long been used
in the computer industry for patterning microchips. Recently, this method
has been applied towards patterning inorganic substrates (e.g., glass)
for neuron growth. Because most cells need a directional scaffold to promote
phenotypical and genotypical expression, microlithography can provide a
precise pattern along which cells can align, function and grow. Although
there are many groups using inorganic substrates, there is little work
on organic or even polymeric substrates For this study, biocompatible polymers
were compressed into thin films, then patterned by adapting conventional
microlithographic techniques. The patterned areas were filled with laminin
to encourage neuronal growth. Using fluorescence microscopy, neuronal alignment
on the patterned surfaces was observed. The polymeric substrates were also
evaluated using x-ray photoelectron spectroscopy to ensure that the lithographic
process did not significantly change the polymer surface.
9:00 AM DD10.2
BIO-INORGANIC COMPOSITES FOR SENSOR APPLICATIONS. R.B.
Bhatia , K.S. Butler, University of New Mexico, Albuquerque, NM; C.J. Brinker,
C.S. Ashley, Sandia National Laboratories, Albuquerque, NM.
Considerable work has been done to date establishing the
retention of bio-activity of enzymes, anti-bodies and whole cells immobilized
within silica gel matrices in liquid media. The demonstration of enzyme-based
molecular recognition and enzyme-catalyzed dye production within silica
hosts is promising for potential bio-sensor applications. However the main
challenge to make bio-sensors is to maintain the sensor selectivity and
sensitivity over the range of temperatures and humidity encountered in
real world environments. Here we report bio-activity of enzymes in xerogels
and aerogels. A two step aqueous sol-gel procedure using sodium silicate
as the precursor was used to encapsulate the enzymes, glucose oxidase and
peroxidase, and dye precursors. These gels were then equilibrated at varying
humidities for three weeks. The sensor scheme involving the reactions of
the enzymes to form a colored product from the dye precursors was demonstrated
within the dried gels. Retention of bio-activity was also shown in the
corresponding aerogels, prepared from the wet gels by supercritical extraction.
Further a vapor phase bio-inorganic sensor was prepared by encapsulating
alcohol oxidase in the silica host matrix.
9:15 AM DD10.3
HIGH SURFACE AREA THIN FILMS FOR DNA ARRAYS. Marc Glazer
, Curtis W. Frank, Dept of Chemical Engineering, Stanford Univ, Stanford,
CA; Richard P. Vinci, Dept of Materials Science, LeHigh Univeristy, Bethlehem,
PA; Jody Beecher, Glenn McGall, Affymetrix, Santa Clara, CA; John Bravman,
Dept of Materials Science, Stanford Univ, Stanford, CA.
DNA Arrays offer a combinatorial approach to DNA analysis
which is likely to have a major impact on biological and genetic research.
Probe based hybridization is carried out in a layer of DNA which is attached
to an inorganic substrate (usually glass). Short strands of DNA (probes)
are grown and patterned on a surface using solution chemistry and photolithography.
Unidentified strands of DNA (target) are then analyzed by hybridization
to the arrays. As in the semiconductor industry, a key to the future development
of the arrays is feature size. To achieve smaller features, we have investigated
high surface area thin films which effectively increase the degree of hybridization
for a 2-D area. Thin inorganic films have been created by annealing and
etching a phase-separating sodium borosilicate glass (7% Na2O,
26% B2O3, 67% SiO2 by wt.) that separates
into soluble (sodium, boron rich) and insoluble (silicon rich) phases during
annealing. The soluble phase is then leached with HF acid, creating a thin
porous surface layer. The surface is then stained and patterned with short,
fluorescently-labeled probes using the process and equipment provided by
Affymetrix. A substantial gain in signal from this process is observed
using confocal fluorescence microscopy. The gain is compared to the actual
density of available sites, which is determined by attaching probes to
the surface, cleaving them in solution, and quantifying with chromatography.
The effects of optical scattering, fluorescence quenching, and the implications
for future work on hybridization of full length probes within the matrix
SESSION DD11: ELECTRONIC PROPERTIES
10:00 AM DD11.1
FABRICATION OF NANOMETER SIZE SILICON WIRE PATTERNS WITH
A SILVER NANOCRYSTAL WIRE SHADOWMASK. Sung H. Choi , Kang L. Wang, UCLA,
Electrical Engineering Dept, Los Angeles, CA; Martin S. Leung, Gary W.
Stupian, Nathan Presser, The Aerospace Corp, Electronics Technology Center,
El Segundo, CA; Sung W. Chung, Sang H. Kim, James R. Heath, UCLA, Dept
of Chemistry and Biochemistry, Los Angeles, CA; Gil Markovich, Tel Aviv
Univ, School of Chemistry, Tel Aviv, ISRAEL.
Chair: Lorraine F. Francis
Thursday Morning, April 8, 1999
Salon 11/12 (M)
Previously, we showed a new method of using silver (Ag)
nanocrystal wires as a shadowmask to produce nanometer-size photoresist
wire patterns. In this abstract, we describe the use of the same technique
to fabricate nanometer-size silicon (Si) wire patterns. In this technique,
organically functionalized Ag nanocrystals (2-100nm) can assemble into
lamella (wire-like) phases. The width of the wires could be controlled
from 20 to 300nm, and for a given set of wires, a narrow distribution of
widths 15-25% could be obtained. The wire patterns can be transferred as
Langmuir-Scheffer (horizontal lift-off) films to the polymethyl methacrylate
(PMMA) coated Si substrates. The height of this nanocrystal pattern was
amplified by immersing the substrate in a solution containing decanedithiol
followed by immersing the substrate into a hexane/nanocrystal solution.
This amplification doubled the height of the wires to about 8nm. The areas
occupied by organic ligands between the nanocrystals in the wire decreased
through a metallization process-ripening of the nanocrystals by mass transfer
between the nanocrystals. The wire patterns were transferred to the PMMA
films by spatially selective electron beam exposure on the Ag nanocrystal
wire shadowmask. 50nm wide Si wire patterns were formed by a subsequent
anisotropic reactive ion etching (RIE) process. Monte Carlo simulation
was done to estimate the electron stopping power for the Ag nanocrystal
shadowmask at low voltage. This technique allows for the use of low energy
electron beam exposure (700V), which reduces the proximity effects and
is suitable for low cost and high throughput fabrication of semiconductor
10:15 AM DD11.2
PROCESSING OF LEAD TITANATE/ORGANIC HYBRID FROM METAL-ORGANIC
PRECURSOR. Toshinobu Yogo , Hiroyuki Ukai, Kaoru Tachibana, Wataru Sakamoto,
Shin-ichi Hirano, Nagoya Univ., Dept of Applied Chemistry, Nagoya, JAPAN.
Ceramic/polymer hybrids attract growing attentions as
new inorganic/organic materials. This paper describes the processing of
PbTiO3/organic hybrid from metal-organic precursor. PbTiO3(PT)
precursor was prepared from lead- organic and titanium alkoxide. IR and
NMR analyses of the precursor revealed the formation of double metal-organics
in solution. The precursor was hydrolyzed and polymerized under the controlled
reaction conditions. The formation conditions of nano-sized PT particles
below 100 centigrade were investigated. The crystalline particles in the
organic matrix were analyzed by Raman spectroscopy, SAD and EDX. The particle
size was found to depend upon the polymerization and hydrolysis conditions.
The electro rheological properties of the hybrid were measured. The hybrid
was shaped into films by heating under pressure. The dielectric properties
of the hybrid film were also evaluated.
10:30 AM DD11.3
ELECTRICAL AND MECHANICAL PROPERTIES OF CARBON BLACK-FILLED
POLYMER COATINGS. Jaime C. Grunlan , David Rowenhorst, Lorraine F. Francis,
William W. Gerberich, Univ of Minnesota, Dept of Chemical Engineering and
Materials Science, Minneapolis, MN.
In carbon black-filled polymer coatings, improved electrical
conductivity is often achieved at the expense of mechanical performance.
Model carbon black-polymer coating systems were prepared to explore the
effects of parameters, such as carbon black loading, polymer modulus, polymer-carbon
interfacial adhesion and coating microstructure on electrical and mechanical
properties. Coatings with poly(vinyl alcohol) [PVA] and poly(N-vinylpyrrolidone)
[PNVP] matrices showed dramatic increases in electrical conductivity at
10-15 vol. carbon black. Beyond the
percolation threshold, PNVP composites achieved a peak conductivity of
3 S/cm at 30 vol. carbon black loading,
which was an order of magnitude higher than that achieved by the equivalent
PVA composite. The elastic modulus, as determined by the Hysitron Triboscope
nanoindenter, increased steadily from 3 GPa for PNVP without any filler
to 6.5 GPa with 30 vol. carbon black.
PVA films followed the same trend but yielded lower moduli at each carbon
black concentration. Composite modulus actually decreased beyond 25 vol.
carbon black, when tested with a dynamic mechanical analyzer, due to macroscopic
defects resulting from exceeding the critical pigment volume concentration
(CPVC). Scanning electron microscopy was employed to evaluate the presence
of defects at each filler concentration. Interfacial adhesion between carbon
and polymer was evaluated using force curves obtained from atomic force
microscopy and Hysitron nanoindentation with carbon-coated tips probing
10:45 AM DD11.4
STRUCTURE AND PROPERTIES OF POLYANILINE- INTERCALATED
GRAPHITE OXIDE NANOCOMPOSITE. Pinggui Liu, Kecheng Gong , South China University
of Technology, Polymer Structure & Modification Research Lab, Guangzhou,
Recently we reported the synthesis of -MnO2-polyaniline
nanocomposite, whose electrical conductivity and thermal
properties had been greatly improved. Graphite oxide, a typical pseudo
two-dimensional solid in bulk form, possesses hydroxyl, carbonyl and ether
groups as functional groups, which cause the low electrical conductivity
of graphite oxide. These groups also make graphite oxide easily absorb
polar molecules and polar polymers to form nanocomposites, especially by
self-assembly in Fendle's paper. In this work, an exfoliation/absorption
process was used to synthesize polyaniline-intercalated graphite oxide
nanocomposite. After reaction, a multiphase product was obtained, this
was proved by XRD, where the strong (001) x-ray diffraction peak of graphite
oxide was completely replaced by some broad, low-intensity deflection between
12-30. FTIR, UV spectra had shown
the existence of polyaniline in form of emeraldine salt. The electrical
conductivity of polyaniline-graphite oxide nanocomposite had been greatly
improved, especially when chemically reduced by aqueous hydrazine hydride
solution, the electrical conductivity of the reduced polyaniline-graphite
oxide was more than 1 order of magnitude higher than that of polyaniline-graphite
oxide at ambient temperature, reaching from 1.4x10-3 S/cm to
3.8x10-2 S/cm. Similarly, the improved thermal stability was
also been proved by thermal analysis.
 K.C. Gong, W. Zhang, ABSTRACTS of 1997
MRS Fall Meeting, No3.9, 332, Boston.
 N.A. Kotov, I. Dekany, J.H. Fendler, Adv.
Mater., 1996, 8, 637.
11:00 AM DD11.5
MICROWAVE DIELECTRIC CHARACTERIZATION OF POLYSILSESQUIOXANE
- POLYANILINE COMPOSITES. J. Obrzut , C.K. Chiang, W.A. Wallace, National
Institute of Standards and Technology, Gaithersburg, MD.
The dielectric properties of the new polysilsesquioxane
- polyaniline composites have been investigated in the broad band frequency
range, up to 20 GHz. The functionalized polyhedral and branched silsesquioxanes
were cross-linked with the oxidized emerdaline-base of polyaniline to obtain
a material of enhanced dielectric properties with a low loss and higher
temperature tolerance. Unlike polyacetylene or poly-para-phenylenevinylene,
polyaniline exhibits asymmetric valence states with the Fermi level shifted
away from the center of the band gap. The presence of de-localized electronic
states with non symmetric charge conjugation at energies less than the
band gap can lead to enhanced polarizability extended to optical frequencies.
We have investigated the effects of protonation of polyaniline on dielectric
permittivity of the composites and compared the results with polymers filled
with ferroelectric powders. We have also examined the DC conductivity and
low frequency dielectric relaxation behavior in relation to the molecular
architecture of the polysilsesquioxane network.
11:15 AM DD11.6
THE ELECTRICAL AND OPTICAL PROPERTIES OF PHENYL-MODIFIED
SiO2 THIN FILMS PREPARED BY SOL-GEL TECHNIQUE FOR MICROELECTRONIC
APPLICATIONS. Chandra S. Desu , Swaroop Kaza, Ramakrishna Vedula, Seshu
B. Desu, Department of Materials Science and Engineering, Virginia Tech,
In the present work, we report a systematic study on the
effect of phenyl modification on lowering the dielectric constant of SiO2
thin films. Both pure and phenyl modified SiO2 thin films have
been prepared by sol-gel technique onto n+(100) Si and p-Si substrates.
Tetraethoxy silane (TEOS) was used for the preparation of SiO2
thin films and the phenyl modification was performed by the addition of
diphenyl diethoxy silane (DDS) to the precursor solution. The as-deposited
films were subjected to annealing treatments at various temperatures in
air. The change in the chemical structure with the composition and the
annealing temperature was observed by FTIR spectroscopy. The film thickness
and the optical properties were measured by spectroscopic ellipsometry.
The dielectric and insulating properties were measured using Al top electrodes
sputter deposited onto the film surface. The refractive index of the films,
measured using ellipsometry indicated a decrease with increasing DDS composition
in the precursor solution. Similarly, the dielectric constant was also
found to decrease with the phenyl modification. All these results indicate
that phenyl modification of SiO2 is a promising approach towards
lowering the dielectric constant.
11:30 AM *DD11.7
MECHANICAL PROPERTIES OF LOW DIELECTRIC-CONSTANT ORGANIC-INORGANIC
HYBRIDS. Robert F. Cook , University of Minnesota, Department of Chemical
Engineering and Materials Science, Minneapolis, MN.
Spin-on glasses, generated by the condensation of an organic-inorganic
hybrid silsesquioxane (SSQ), have great potential as low dielectric-constant
semiconductor interconnection materials. After curing and condensation
SSQ materials consist of an amorphous, inorganic, -Si-O-Si- bridging network
with organic, non-bridging -Si-R side groups. Relative dielectric constants
in the range 2.5-3.3 are obtained for SSQ materials, depending on the curing
conditions, and compare with 4.0 for conventionally-used fused silica.
The non-bridging side groups significantly disrupt the SSQ network, occupying
more than 25% of the Si bonds, and lead to materials that are considerably
less stiff, hard and tough than fused silica. Perhaps more importantly,
SSQ materials have thermal expansion coefficients greater than that of
the intended Si substrate and therefore finish curing in a state of residual
tension, leading to a susceptibility to stress-corrosion cracking. In this
talk the development of properties (dielectric and mechanical) during curing
of SSQ spin-on glasses is considered and the properties of hydridi-, methyl-,
and phenyl-substituted SSQ materials compared. Various toughening schemes
involving both organic and inorganic additions will be discussed.
SESSION DD12: MECHANICAL PROPERTIES AND APPLICATIONS
1:30 PM *DD12.1
THE ACID-BASE ENERGETICS OF ADHESION IN COMPOSITE MATERIALS.
John C. Berg , University of Washington, Dept of Chemical Engineering,
Chair: Lisa C. Klein
Thursday Afternoon, April 8, 1999
Salon 11/12 (M)
Filled polymeric composites are investigated to assess
the role of acid-base effects on the adhesion between the filler particle
surface and the matrix polymer and on the mechanical properties of the
composites. The surface of the filler material is systematically modified
using silane coupling agents, and a variety of surface characterization
techniques are used to determine their surface energetics and acid-base
properties. Adhesion properties are determined by a new direct method in
which a single spherical filler particle is embedded into the matrix. The
single-particle composite is subjected to uni-axial tension until interfacial
failure occurs at one of the poles, yielding the stress at failure and
a characteristic cap angle, without edge and end effects. Measured interfacial
strengths correlate on one hand with acid-base effects determined independently,
and on the other hand with the mechanical properties of highly-filled composites
of the same components, as determined in beam deflection tests.
2:00 PM DD12.2
HYBRID ORGANIC-INORGANIC COATINGS BASED ON COLLOIDAL
SILICA. M.W. Daniels , L.F. Francis, Univ. Minnesota, Dept. of Chemical
Engineering and Materials Science, Minneapolis, MN.
Coatings from ceramic colloids are widely used due to
the flexibility and convenience offered by suspensions and the advantages
gained from ceramic properties such as hardness and index of refraction.
However, ceramic coatings made from colloidal suspensions generally have
poor properties (wear resistance, critical cracking thickness, adhesion)
unless high processing temperatures or additives are used. Organic additives
such as silane coupling agents and binders give coatings the desired mechanical
properties. This presentation will focus on studies of how these additives
affect the microstructure and properties of colloidal silica coatings.
Important coating features studied include porosity, wear resistance, cracking
behavior, and adhesion. Microstructure and properties are influenced by
composition, pH, processing time and temperature, and components. A better
understanding of the effect of these variables is gained through study
of the reactions in the coating solution, which occur before and during
drying. Adsorption of silane coupling agent was studied and combined with
observations of reactions between coupling agents to develop an explanation
of how the final microstructure developed. Use of UV-cured cross-linkers
was shown to improve wear resistance, while amine crosslinkers increased
2:15 PM DD12.3
SOL-GEL ANTIFOGGING COATINGS ON POLYMER SURFACES. Hermann
Schirra , Thomas Mueller, Helmut Schmidt, Institut fuer Neue Materialien
gem. GmbH, Saarbruecken, GERMANY.
Objective of these investigations was the development
of polymer surface coatings, which are characterized by a good wettability
of water and oleophilic liquids as well as a long term stable antifogging
effect. Scratch resistant nanocomposite coatings based on an epoxysilane/methacrylsilane/boehmite
system have been chosen as basis material. By an incorporation of nonionic
or cationic based hydrophilically active components the hydrophilicity
of these systems could be increased with achieving contact angles against
water down to 5 and excellent
antifogging properties. The best results were obtained, if the hydrophilic
components being linked to the backbone as well as surfactants being able
to diffuse through the network were used at the same time. The immobilized
surfactants provide the basis ambiphilicity of the system and the diffusible
components are able to react to hydrophobic as well as to hydrophilic contaminates
on the surface. By optimization of the system composition, coatings could
be developed with material properties between highly flexible (e.g. for
the coating of foils) and abrasion resistant with haze values of 15-20%
after 1000 cycles taber-abrasion test (CS 10F, 500 g load). With all substrates
(PC, PET, PMMA) excellent adhesion (crosscut >95/100, tapetest as well)
resulted after a suitable way of pretreatment (primer, corona, pretreatment,
flame). In the case of PMMA a nanocomposite coating material could be synthesized
with a crosscut/tapetest >95/100 only with an alcoholic cleaning of the
surface. The long term hydrophilicity was proven in a 40C
water exposition test. All coatings showed contact angles against water
of < 30 ° after 7 and 14 d exposition without any delamination of
2:30 PM DD12.4
ABRASION RESISTANT ORGANIC/INORGANIC HYBRID SOL-GEL COATINGS
ON PLASTICS. C.M. Chan and G.Z. Cao, University of Washington, Department
of Materials Science and Engineering, Seattle, WA.
We investigated abrasion resistant organic/inorganic hybrid
sol-gel coatings on plastics. Silica network was modified by incorporation
of organic components and transition metal oxides so as to modify thermal
and mechanical properties of the coatings. Highly dense coatings (up to
99% theoretical density) were obtained using in-situ low temperature (below
150 °C) densification techniques, that included enhanced evaporation
of solvent, ultra-violet (UV) irradiation promoted surface condensation,
and infrared (IR) assistant structural relaxation. Various surface treatments
were applied to achieve good adhesion of sol-gel coatings on plastics.
Nanoindentation analysis revealed that the hybrid coatings had a surface
hardness of 2.5 GPa, approximately one order of magnitude higher than that
of the plastic surface. In addition, ellipsometry and nanoindentation analyses
indicated that both the density and hardness varied with the depth of the
2:45 PM DD12.5
SOL-GEL HYBRID MATERIALS FOR POWDER COATING TECHNOLOGY
FOR TRANSPARENT ABRASION RESISTANT FILMS. S. Sepeur , J. Muhle, H. Schmidt,
Institut fuer Neue Materialien gem. GmbH, Saarbruecken, GERMANY.
Sol-gel coating powders were recently prepared by hydrolysis
and controlled polycondensation from mixtures of organically modified silanes
and organic crosslinking-agents with an optional incorporation of nanoparticles.
After evaporation of the solvent or precipitation in an excess of water,
drying under vacuum and grinding, solid materials were obtained. The resulting
non-sticky powders with a melting range between 85-100C
showed thermosetting behavior after thermal densification, which was proved
by DSC-measurements. At temperatures between 100-150C
the minimum melt-viscosities of the inorganic-organic nancomposites ranged
between 0.1-150 Pas. For coating,
the powders were employed by a corona-charging spray gun, and transparent
dense coatings with thicknesses between 20-40 m
were obtained. The powder coatings showed good primerless adhesion to the
surface of aluminium sheets (Al 99.5, AlMg3), which was determined
using cross-cut (grade 0/1) and tape test (grade 4B/5B). The surface hardness
of the sol-gel powder coatings was well adjustable by use of nanoparticles
(universal-hardness: 160-285 N/mm2, Buchholz-resistance of indentation:
120-140). In addition the coatings showed an excellent abrasion resistance,
which was determined by taber-abraser test (weight loss method). After
1000 cycles of abrasion with certain wheels (CS-10 F), the material loss
ranged only between 7-14 mg. The corrosion resistance of the coatings was
examined by salt spray test. After 2000 h in the test chamber the coated
aluminium sheets (Al 99.5 and AlMg3) showed little formation
of blister (m1/g1), but no infiltration at the scratch and no reduction
of the adhesion after the loading in the corrosive medium, which was proved
by cross-cut (grade 0/1) and tape test (grade 4B/5B). The running outdoor
weathering measurements (location: Uni-Campus Saabruecken, position: south)
provided no change of the coating appearence and no infiltration at the
scratch after an exposure time of 2400 h.
3:30 PM DD12.6
TEAR STRENGTHS OF POLY(DIMETHYLSILOXANE) NETWORKS REINFORCED
WITH IN-SITU PRECIPITATED SILICA. Chandima Kumudinie, James E. Mark , Department
of Chemistry and the Polymer Research Center, The University of Cincinnati,
The tear strengths of in-situ filled poly(dimethylsiloxane)
(PDMS) networks were investigated using trouser-tear tests. The filled
PDMS networks were prepared by the simultaneous curing and in-situ precipitation
technique, the silica reinforcing phase being obtained by the hydrolysis
and condensation of tetraethylorthosilicate present in excess of that required
for the chain end-linking process. Transmission electron micrographs showed
well dispersed and unagglomerated silica particles, and thermogravimetric
analysis indicated that the silica particles gave some improvements in
thermal stability. In the tearing tests, stick-slip tearing was observed
at higher rates, especially for the filled networks. The tear strengths
were found to increase with increase in the amount of silica incorporated,
with the largest increases occurring at the lower silica contents.
3:45 PM DD12.7
MECHANICAL PROPERTIES OF SOLUBLE POLYMER/SILICA GEL HYBRIDS.
L.C. Klein , J. Van Wert and C.L. Beaudry, Rutgers University, Ceramic
& Materials Engineering, Piscataway, NJ.
Strengths have been measured for silica gels prepared
with poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc). The modulus
of rupture was determined using standard three-point bending in a mechanical
tester. The samples were prepared by mixing tetraethylorthosilicate with
the polymers dissolved in water (PEO) or water/ethanol(PVAc). Molecular
weights between 200 and 8000 were used for PEO. Substitutions of the polymer
for silica represented between 5 and 50
on a weight basis. Those compositions that were transparent were selected
for testing. Samples that were translucent or opaque were indicative of
phase separation, and for that reason, were not suitable for testing. All
samples were allowed to gel in plastic tubes. The tubes were capped initially,
but the caps were removed after specified periods of aging, from 1 to 24
hours. All samples were thoroughly dried. In these systems, the interactions
between the polymer and the silica network are largely through hydrogen
bonding, between ether oxygens in PEO and silanols and between hydroxyls
in PVAc and silanols. The extent of the bonding increases with increasing
aging time, as indicated by an almost linear increase in the modulus of
rupture. The increase for PEO was greater than for PVAc. Among PEO samples,
the strengthes were higher for higher molecular weights at the same weight
fraction, but the increase with time was about the same. The pH and the
how it was controlled had some effect as well. Most samples broke in the
middle and showed brittle fracture. Some samples showed slight plasticity
during failure. Both the choice of polymer and processing conditions influenced
the strength of these hybrids.
4:00 PM DD12.8
VISCOELASTIC RESPONSES OF INORGANIC-ORGANIC HYBRIDS POLYMERS.
Andre Lee , Michigan State University, Dept. of Materials Science and Mechanics,
E. Lansing, MI.
The properties of nano-structured plastics are determined
by complex relationships between the type and size of the nano-reinforcement,
the interface and chemical interaction between the nano-reinforcement and
the polymeric chain, along with macroscopic processing and microstructural
effects. In this paper we investigated the thermal and viscoelastic property
enhancement on crosslinked epoxy using two types of inorganic nano-reinforcements,
namely organoion exchange clay and polymerizable polyhedral oligomeric
silsesquioxane (POSS) macromers. Glass transitions of these nano-composites
were studied using differential scanning calorimetry. Small strain stress
relaxation under uniaxial deformation was examined to provide insights
into the time-dependent viscoelastic behavior of these nano-composites.
Since the size of POSS macromer is comparable to the distance between molecular
junctions, hence as we increase the amount of POSS macromers, the glass
transition temperature, Tg, as observed by DSC increase. However for epoxy
network reinforced with clay, we did not observe any effect on the Tg due
to the presence of clay reinforcements. In small strain stress relaxation
experiments, both types of reinforcement provided some enhancement in creep
resistance, namely the characteristic relaxation time as determined using
a stretched exponential relaxation function increased with the addition
of reinforcements. However, due to different reinforcement mechanisms,
enhancement in the instantaneous modulus was observed for clay-reinforced
epoxies, while the instantaneous modulus was not effected in POSS-epoxy
4:15 PM DD12.9
PREPARATION AND PROPERTIES OF PVC-SILICA COMPOSITES USING
DIFFERENT CATALYSTS VIA SOL-GEL PROCESS. Khan M. Asif , Kansas State University,
Dept of Chemistry, Manhattan, KS; M.I. Sarwar and Z. Ahmad, Dept of Chemistry,
Quaid-i-Azam University, Islamabad, PAKISTAN.
Novel micro-composites of Polyvinyl chloride (PVC) and
silica were prepared using sol-gel technique. Different catalysts were
used during the hydrolysis/condensation of tetraethylorthosilicate (TEOS)
for the in-situ generation of silica network in the PVC matrix. Thin and
transparent films were obtained by casting and solvent evaporation method.
Mechanical properties of these films up to 15 wt.% silica contents using
different catalysts were studied. The results showed an increase in the
Young's modulus, length at rupture and toughness of the unplasticised PVC.
However, the stress at yield point and stress at rupture decreased with
the addition of silica contents. Scanning electron microscopy (SEM-EDAX)
studies were also performed on the samples.
SESSION DD13: OPTICAL PROPERTIES AND APPLICATIONS
8:30 AM *DD13.1
ORGANIC-INORGANIC HYBRID MATERIALS PROCESSING AND APPLICATIONS.
Helmut K. Schmidt , Institut fuer Neue Materialien, Saarbruecken, GERMANY.
Chair: Hyunjung Shin
Friday Morning, April 9, 1999
Salon 11/12 (M)
Organic-inorganic hybrid materials have become an interesting
group of new materials which now are entering the field of industrial application.
This has been realized for the first level hybrids with molecular networks,
and is now being realized with the second level hybrids with mesoscopic
scales. The combination of first and second level hybrids are of interest
since solid state physical properties attributed to nanoparticles (or colloids)
can be introduced into the materials which still show high optical transparency.
So-called polymerizable nanoparticles have been developed by in-situ coating
of sol-gel derived colloids from SiO2, TiO2, ZrO2
with polymerizable grouping containing ligands and matrix compatible nanoparticles
have been synthesized by coating them with organofunctional groupings fitting
to polymeric matrices (ZrO2, ITO). These particles have been
used for the fabrication of UV curable or thermally curable interference
multilayers, for the fabrication of volume holograms, grated index lenses
and highly abrasive UV-curable coatings for plastics. In addition to the
in-situ preparation of the nanoparticles by sol-gel reactions, it also
was possible to produce nanoparticles by chemical - optional including
hydrothermal - processing and surface modification afterwards in form of
redispersible powders, as shown with ZrO2 and ITO. The use of
ITO nanoparticles in hard coatings based on epoxy silane/boehmite compositions
led to IR absorption layers with an effective energy flow reduction to
about 50, and by use of ZrO2
particles, refractive index matching hard coatings for ophthalmic applications
have been obtained.
9:00 AM DD13.2
PHOTOCHROMIC ORGANIC-INORGANIC HYBRID NANOCOMPOSITE HARD
COATINGS WITH FAST SWITCHING PROPERTIES. M. Mennig , K. Fries and H. Schmidt,
Institut fuer Neue Materialien gem. GmbH, Saarbruecken, GERMANY.
A sol-gel hybrid coating system has been developed, which
is based on an epoxysilane as network former, different bisepoxides as
spacer, organic amines as thermal cross-linker and surface modified ceramic
nanoparticles as filler. The compatibility of the matrix systems has been
tested with about 30 commercially available photochromic dyes and thus
the preparation of photochromic coatings with neutral tints is possible
by mixing different dyes. Photochromic coatings with blue, yellow, red,
green, violet and neutral tints were prepared on flat PC (polycarbonate),
curved CR 39 (allyl substituted polycarbonate) substrates and PET-foil
(polyethylenterephthalate) by spray and spin coating respectively and cured
for 2 h - 5 h at 80C - 130C
and on different kinds of paper by spray coating and air curing. The photochromic
coatings show the following properties: the transmittance changes reversibly
between 80 and 20
with half fading times of about 2 s - 20 s (comparable to the half fading
time of the appropriate dye in ethanolic solution) after UV irradiation
for 15 s with 10 mW/cm2. The coatings are stable against organic
solvents and show a scratch hardness of about 15 g (scratch test with Vickers
indenter, coating thickness 10 m).
The addition of only 3 wt SiO2
nanoparticles increases the scratch resistance of the coatings to about
30 g without changing the fast kinetics of the incorporated photochromic
dye(s). The long term stability of the photochromic dye(s) in the matrix
system has been considerably improved by the introduction of additives
like antioxidants, HALS (Hindered Amine Light Stabilizer) and UV stabilizers.
The half lifetime (decay to 50 of the
initial photochromic intensity) of a blue spirooxazine dye thus could be
increased from 20 hours in a dry suntest (75 mW/cm2) without
any additive up to 200 hours with an UV absorber (Tinuvin 327) as a stabilizer,
which is assumed to be sufficient for ophthalmic and many decorative applications.
9:15 AM DD13.3
SOL-GEL AR MULTILAYER COATINGS THROUGH UV-POLYMERISABLE
CERAMIC NANOPARTICLES. M. Mennig, P.W. Oliveira , H. Schmidt, Institut
fuer Neue Materialien gem. GmbH, Saarbruecken, GERMANY.
A new synthesis and processing route to multilayer interference
coatings on plastic (like PMMA, polycarbonate and polyester) and glass
substrates has been developed. For this purpose alcoholic sols of surface
modified (3-glycidoxypropyl trimethoxysilane, GPTS) SiO2 - and
TiO2 nanoparticles with particle sizes of 10 nm and 4 nm respectively
were synthesized by acid catalysed hydrolysis and condensation of the appropriate
alkoxides. In order to control the particle growth and to avoid agglomeration
GPTS was added as a surface modifier. By the combination of index matching
and photopolymerization, interference filters have been fabricated. The
interference coatings on polycarbonat show excellent adhesion (GT 0) to
the substrates and cause a promising improvement in the mechanical properties
of the substrate. The interference coatings do not show delamination or
defects after boiling water test (H2O + 5 wt
NaCl, 1 h). The mechanical and optical properties of the interference filter
were not changed after sun test by 760 W/m2 and 275 h. An antireflecting
(AR) coating filter with 3 quarterwave layers and an NIR reflective interference
filters with 5 layers were produced on float glass substrates. Each layer
was deposited by dip- or spin-coating with subsequent UV-curing with an
energy density of 2.5 J/cm2, and the layer stack was thermally
densified at 450C for 10 min.
80 cycles of rubber test without damage could be obtained. The mechanical
and optical properties of the interference filters did not change after
sun test with 760 W/m2 for 320 h.
9:30 AM DD13.4
FABRICATION OF GRIN LENSES BY CONTACTLESS ELECTROPHORETIC
GRADIENT FORMATION IN TRANSPARENT NANOCOMPOSITES. P.W. Oliveira , M. Mennig,
H. Schmidt, Institut fuer Neue Materialien gem. GmbH, Saarbruecken, GERMANY.
A new approach to effective radial gradient refractive
index (GRIN) lenses has been developed. It is based on the electrophoresis
of ZrO2 and SiO2 nanoparticles with opposite surface
charges (-potential) in a solvent
free organic-inorganic hybrid matrix, synthesized from tetraethylene glycol
dimethacrylate (TEGDMA), methacryl silane (MPTS) and a complex of zirconium
n-propylat (ZR) with methacrylic acid (MA). A DC-electric field of 200
V/cm is applied by a set of ring electrodes on top and bottom of a cylindrical
mold containing the matrix sol. The refractive index profile is measured
in situ as a function of time by interferometry. The refractive index profile
can be conserved by photopolymerisation of the matrix. The resulting concentration
profiles of ZrO2 and SiO2 are calculated by computer
simulation based on electrophoretical diffusion theory and they are measured
by EDX analysis, showing excellent agreement to the theoretical results
and a parabolic refractive index gradient is obtained in very good approximation.
By this method it is possible to obtain 1 cm radial GRIN lenses with a =0.07
within 5 h.
9:45 AM DD13.5
SOL-GEL DERIVED TITANIA/ORMOSIL COMPOSITE THIN FILMS
FOR OPTICAL WAVEGUIDE APPLICATIONS. Wenxiu Que, Y. Zhou, Y.L. Lam, Y.C.
Chan, C.H. Kam and H.X. Zhang , School of Electrical and Electronic Engineering,
Nanyang Technological University, SINGAPORE.
In this paper, we report the preparation of high optical
quality sol-gel waveguide films based on a newly developed recipe to incorporate
organic molecules into the inorganic sol-gel glass matrix. The film is
derived from a sol that has a high titanium content in an organiclly modified
silane (ORMOSIL), namely, -Glycidoxypropyltrimethoxysilane.
We have shown that using spin-coating or dip-coating and low temperature
baking, a single coating layer can have a thickness of more than 1 .
When such a single layer film is deposited on a microscope glass slide
or a piece of silicon with a buffer-cladding layer, it is able to support
the guiding of optical waves. We have characterized the film using atomic
force micriscopy, X-ray diffractometry, thermal gravimetric analysis, and
Fourier transform infrared spectroscopy and have studied the properties
of the waveguide film, including the microstructural properties, the chemical
bonding properties, and the optical properties. Based on these experimental
results, we found that a heat-treatment at a temperature below 200C
is necessary to attain a dense film with low absorption or high tranmission
in the visible and near infrafed range. It has also been noted that a purely
inorganic and crack-free silica-titania film can be obtained after baking
the titania-ORMOSIL composite film at 500C
or higher. At the conference, we will present the details of our study
and discuss the implications of our research.
10:30 AM DD13.6
PHOTOPHYSICAL PROCESSES IN HYBRID MATERIALS OF CONJUGATED
POLYMERS AND DYE-SENSITIZED TiO2. Thomas K. Daeubler , Ullrich
Scherf, Dieter Neher, Max-Planck-Institute for Polymer Research, Mainz,
GERMANY; Steffen Pfeiffer, Hans-Heinrich Hoerhold, Univ. Jena, Inst. for
Organic Chemistry and Macromolecular Chemistry, Jena, GERMANY; Ireneusz
Glowacki, Jacek Ulanski, Technical Univ. Lodz, Div. of Polymer Physics,
In the last few years the request for inexpensive materials
for use as efficient xerographic layers, photorefractive devices and large
area solar cells has stimulated considerable research activities on photogeneration
of charge carriers in soluble conjugated polymers. Various sensitizers
have been used to increase the low intrinsic generation efficiencies in
these materials. A new, attractive approach to long wavelength sensitization
and enhancement of generation efficiencies is the use of dye coated semiconductor
nanoparticles.  We present steady state photoconductivity experiments
performed on solid films of inorganic/organic composites. The photoresponse
of devices with different polymer hosts proof that an enhanced and spectrally
broadened photogeneration of charge carriers requires electron transfer
from the polymer to the dye. While for low nanoparticle concentrations
photoaction spectra exhibit a pronounced peak at the absorption edge of
the polymer, signatures due to the absorption of the Ru-dye are observed
for high TiO2 contents. Photocurrents and the shape of the photoaction
spectra are only weakly affected by replacing anatase/brookite TiO2
with rutile TiO2. The I-V-characteristics of the composites
indicate an enhanced injection of electrons from both electrodes into the
dye coated nanoparticles and that percolation networks of nanoparticles
are formed. Charge collection efficiencies exceeding 100% are observed
and explained by photoconductivity gain phenomena. These effects might
be particularly enhanced in the composite devices. Since transport of the
two kinds of charge carriers occurs in different phases, reducing the probability
for charge carrier recombination.  M. Kocher, T.K. D, E. Harth, U. Scherf,
A. G, D. Neher, Appl. Phys. Lett. 72(5), (1998) 650 - 652
10:45 AM DD13.7
SYNTHESIS & CHARACTERIZATION OF OPTICALLY-ACTIVE
LANTHANIDE-DOPED HYBRID INORGANIC-ORGANIC SYSTEMS. R.E. Taylor-Smith ,
K.M. Choi, Bell Laboratories, Lucent Technologies, Murray Hill, NJ.
The materials chemistry of sol-gel-derived inorganic-organic
molecular composites offers significant potential for molecular-level systems
design. One focus in this arena is the chemical design and microstructural
engineering of optically-active systems. We report the generation of rare-earth-doped
inorganic-organic hybrids, based on a bridged-polysilsesquioxane architecture.
Derived from lanthanide precursors such as erbium isopropoxide, which we
co-condense with the requisite silsesquioxane monomer, these systems exhibit
significant optical activity. In experiments on hybrids doped with erbium,
we conclusively demonstrate that the 4I13/2 => 4I15/2
transition results in strong fluorescence at wavelengths in the vicinity
of 1540 nm, from stimulation with 488 nm radiation. We discuss materials-driven
impacts of the bridged-polysilsesquioxane architecture on system complexities
arising from the solution sol-gel route which would affect fluorescence
efficiencies and luminescence levels, such as hydroxyl impurities and clustering-effects.
11:00 AM DD13.8
OPTICAL SPECTROSCOPY OF ORGANIC-INORGANIC PEROVSKITES.
C.R. Kagan , D.B. Mitzi and K. Chondroudis, IBM T. J. Watson Research Center,
Yorktown Heights, NY.
We report on the optical properties of self-organizing
hybrid materials based on alternating anionic perovskite sheets and stereoregular,
cationic organic layers. The inorganic sheets extend in 2D and behave like
semiconductor quantum wells, having excitons with large binding energies
and oscillator strengths. Choosing the chemistry of the perovskite sheet
(for example, A2MX4 where A= organic cation, M= metal
such as Pb or Sn, and X= anion such as Cl,Br, I) tunes the optical absorption
and photoluminescence of the inorganic sheet through the visible. We correlate
the structure and optical properties of the organic-inorganic hybrids as
a function of temperature for both thin films and single crystals. Tailoring
the electronic structure of both the organic and inorganic layers may be
used to control the interaction between the layers of the hybrid and the
color of its emission.
11:15 AM DD13.9
OPTICAL SENSING WITH SOLVATOCHROMIC DYES INCLUDED IN
ZEOLITE HOSTS. Julia L. Meinershagen and Thomas Bein, Department of Chemistry,
Purdue University, West Lafayette, IN.
The inclusion of Solvatochromic dyes in the crystalline
cage system of zeolite hosts has been explored for the design of highly
selective optical sensors. Approaches such as in situ synthesis, ion exchange
as well as direct adsorption into zeolite hosts were demonstrated for dye
encapsulation. Several solvatochromic dyes, showing different response
mechanisms to their environment, were explored for sensing applications.
Dramatic, reversible shifts in the absorbance and fluorescence spectra
of the encapsulated dyes in the presence of various analytes were observed.
For example, we demonstrate the inclusion synthesis of Nile Red in zeolites
from 1-naphthol and 6-nitroso-3-diethylaminophenol (as a limiting reagent)
in acidic environments. In siliceous faujasite, the stable hydrophobic
dye/zeolite ensemble shows a hypsochromic shift of ca. 70 nm in the diffuse
reflectance spectrum upon exposure to ethanol and acetone vapors at low
pressures. Size exclusion was explored by using a more bulky molecule such
as 2-4-di-tert-butylphenol. While a wavelength shift in solution is observed
from the interaction of Nile Red with 2-4-di-tert-butylphenol, it does
not respond when encapsulated in the zeolite. By restricting highly solvatochromic
dyes into zeolite hosts, we demonstrate specificity towards various molecules,
as well as size selectivity that can be applied in chemical sensing.
11:30 AM DD13.10
INORGANIC QUANTUM DOT - ORGANIC DENDRIMER NANOCOMPOSITE
MATERIALS. Kelly Sooklal, Jinman Huang, Catherine J. Murphy , Univ of South
Carolina, Dept of Chemistry and Biochemistry, Columbia, SC; Leo Hanus,
Harry J. Ploehn, Univ of South Carolina, Dept of Chemical Engineering,
Semiconductor quantum dots are of great current interest
for their optical properties. We have developed a method for preparing
CdS quantum dots in commercially available PAMAM Starburst dendrimers.
The resulting dots are exceptionally stable and emit brightly in the blue.
The CdS quantum dots have optical signatures that suggest they are very
small (20 Å, yet transmission
electron microscopy and dynamic light scattering studies suggest that that
the dots and dendrimers aggregate into nearly micron-scale flocs that are
very soluble. Thin films are readily cast from such solutions, and the
emission remains intact. The dot-dendrimer nanocomposites can be captured
in a silica sol-gel matrix to yield a stable, bright blue-emitting glass.
Compared to other stabilizing agents, the dendrimers protect the CdS quantum
dots from coalescence into larger dots. Pre-aggregation of the dendrimers
also influences the size and emission of the resulting CdS dots.
11:45 AM DD13.11
THERMOCHROMIC COMPOSITIONS BASED ON HYBRID ORGANOINORGANIC
PVA COMPLEXES. T.G. Lazareva , E.P. Kalutskaja, Institute of General and
Inorganic Chemistry of the National Academy of Sciences of Belarus, Minsk,
The possibility of forming the thermochrornic compositions
based on hybrid hydrated organoinorganic complexes of polyvinyl alcohol
(PVA) and the basic principles of their formation are discussed. The methods
of IR spectroscopy as well as the differential and sorption methods have
been adopted to study structural peculiarities or the complexes depending
on the Co2+ concentration. A role of anions, with Cl -,
NO3- taken as an example, in the complex formation
is evaluated. The processes of hydration and the changes in the structure
of the PVA - Co2+ complexes upon sorption are investigated.
The basic information on the structure of PVA - Co2+ complexes
is obtained, first of all, from an analysis of the absorption region of
OH-groups in the IR spectra as well as absorption bands of the metal. A
shift of the absorption region of the OH-groups toward a low-frequency
region is noticed, new bands with maxima at 3160 cm-1 and 500
cm-1 are detected. A conclusion is made about formation of the
PVA - Co2+ - Cl- compound, in which a metal cation
interacts with an oxygen atom of the OH-group via donor-acceptor bonds,
while Cl- anions participate in formation of stable hydrogen
bonds with the OH-groups of PVA with respect to the oxygen atom. The possible
schemes of complex formation are given. It is established that the complex
formation leads to a decrease in the degree of crystallinity of the polymer
matrix from 10 to 30 depending on a
metal concentration, a decrease of the share of syndio-and heterotactic
phases. Introduction of Co2+ ions into the PVA matrix causes
the considerable enhancement of sorption of water molecules starting from
30 relative elasticity of water vapor
upon sorption. In this case, if in the initial stages of hydration water
molecules are bounded with the OH-groups of PVA, in the intermediate stages
(>30 relative elasticity of water vapor)
water molecules enter the coordination sphere of the cation by partially
destructing the PVA - Co2+ bonds and forming large hydrated
structures with the spectroscopic features typical for the spectra of aqueous
solutions forming the O...H...O fragments. Reversibility
of the sorption processes due to the sorption-desorption-sorption stages
is also considered. The compositions are recommended as promising thermochromic