Ultrafast Excited State Absorption in Chromophore-Functionalized Chiral Polybinaphthalenes

Nov 29, 2018 - 7:00 PM -  CM04.11.05
Hynes, Level 1, Hall B
Leonardo de Boni1,Jonathas Siqueira1,Marcelo Vivas2,Cleber Mendonca1

Institute of Physics of São Carlos - University of São Paulo1,Universidade Federal de Alfenas2
The study of ultrafast chirality dynamics in the excited state has received considerable interest over the past years. Chiral polymers show particularly interesting properties for applications in emerging field of chiral photonics. Chromophore-functionalized polybinaphthalenes are an interesting class of chiral polymers given their high chirality in the ground state. Chromophore-functionalized polybinaphthalenes show a tree-like structure: they are composed of a rigid, rod-like backbone to which flexible chromophores are attached. This tree-like supramolecular architecture, the chromophores (branches) are attached to a rigid backbone (trunk), diminishes and even excludes dipolar interactions between the chromophores. In a previous study on donor-embedded polybinaphthalenes, it was demonstrated that they are a very interesting class of polymers since the dipolar interactions between the chromophores are excluded in these materials and chiral contributions are present. The spectral dependence and ultrafast dynamics of excited state absorption of four different chromophore-functionalized polybinaphthalenes, were characterized by femtosecond absorption transient spectroscopy as a first step towards the characterization of their chirality dynamics in the excited eletronic state.<br/>In order to better understand the origin of chirality in this class of polymers, we aim at studying their chirality in the excited state. An initial study in this direction was the characterization of their excited state absorption and dynamics via femtosecond transient absorption technique for four chiral polybinaphthalenes. Excited state absorption (ESA) spectroscopy at femtosecond time scale was carried outto measure the relaxation times and absorption spectra of their electronic excited states. Femtosecond time-resolved ESA experiment was implemented using 150-fs pulses (775 nm) from a regenerative Ti:sapphire. ESA spectra and dynamics measurements were performed using the pulse at 387.5 nm (second harmonic of 775 nm) as a pump pulse and a white light continuum (400 - 700 nm) as a probe. We obtained excited state characteristic deactivation times shorter than 100 ps and characterized the spectral dependence of their excited state absorption. The data obtained in this study will assist us in the characterization of the chirality ultrafast dynamics on the electronic excited state of this novel class of chiral polymers.