Marcos Cardoso 1 , Adriano Otuka 1 , Gustavo Almeida 1 , Josiani Stefanelo 1 , Antonio Zanatta 1 , Cleber Mendonca 1
1 Sao Carlos Institute of Physics, University of Sao Paulo Sao Carlos Brazil
Several potential applications have been suggested for carbon nanotubes, including electrical applications and mechanical reinforcement for composites. When combined with other materials, these nanotubes can provide improvements and functionalization of structures made from various materials. Several methodologies have been applied to produce composites devices, mainly using polymeric matrices. Photopolymerization techniques, using linear or nonlinear optics phenomena, have been frequently used to fabricate composites in nano or micro scale . Multiphoton absorption polymerization (MAP) have been widely used for this purpose. Thus, the objective of this work is to focus on the production f-SWCNT/acrylate micro-composites using MAP and the investigation of the mechanical and electrical properties, comparing with the pure polymer. To fabricate f-SWCNT/acrylate micro-composites we used a mixture in equal proportions of two three-acrylate monomers. These monomers are mixed with an aclyphosphine oxide photoinitiator. Functionalized SWCNT dispersed in water are added to liquid resin. After solvent evaporation, this resin is placed between a glass substrate and a cover slip for the microfabrication process. The laser source used is a Ti:Sapphire oscillator operating at a repetition rate of 86 MHz delivering 100 fs pulses, centered at 780 nm. The laser beam is focused through a microscope objective into the liquid resin and scanned during the photopolymerization procedure. As a result, fabricated composites present good surface quality and integrity, even when a high SWCNT concentration (1.00 wt%) was employed. Raman analysis indicates a good distribution of SWCNT throughout the microstructure. Phase AFM images for the pure polymer, as well as for the composite containing f-SWCNT indicate changes in the micro-mechanical properties of the structures containing SWCNT, such as in the elastic modulus and viscoelasticity. Besides, nanoscratches mechanical essays are being made using AFM to show the benefits of reinforcement with nanotubes. The electrical conductivity of these composite is higher than pure polymer. Even using low concentration of f-SWCNT in these composites (0.01 wt%), we observe a significantly improvement electrical conductivity. The results obtained in this work show that SWCNT incorporated in acrylate polymers might be useful to provide microstructures with mechanical and electrical improvement, opening new possibilities for microdevices application. The authors acknowledge FAPESP (Grants # 2011/12399-0, 2011/23587-1 and 2014/21439-1), CNPq, CAPES and the Air Force Office of Scientific Research (FA9550-07-1-0374) for financial support and Andre Romero for technical assistance.
 Otuka, A. J. G., et al., Single-Walled Carbon Nanotubes Functionalized with Carboxylic Acid for Fabricating Polymeric Composite Microstructures. Journal of Nanoscience and Nanotechnology, 2015. 15(12): p. 9797-9801.