Photo-induced dichroism and surface relief gratings of two novel branched side-chain azo polyelectrolytes

Novel polyelectrolytes (PBANT-AC and PBACT-AC) functionalized with branched side-chains containing electron donor-acceptor type azo chromophores have been synthesized through a post- polymerization azo-coupling reaction route and characterized by H-1-NMR, FTIR and UV-Vis spectroscopy. The degree of functionalization ( DF) of PBANT-AC and PBACT-AC were 17% measured by elemental analysis. The degree of polymerization and its distribution were determined by GPC to be X-n = 588 with a polydispersion index 1.3. Glass transition temperatures of PBANT-AC and PBACT-AC were estimated from DSC thermogram to be 139degreesC and 159degreesC, respectively. Dichroism was optically induced in the spin-coated films of the two polymers under the irradiation of a polarized Ar+ laser beam, at 488 nm. The resulting dichroism was detected from UV-Vis spectra, which exhibited a long-term stability at room temperature. The orientational order parameters obtained were 0. 12 and 0.09 for the PBANT-AC and the PBACT-AC films. Surface relief gratings were optically inscribed upon exposure to an interference pattern of Ar+ laser beams at modest intensities. The surface modulations were about 45 nm and 80 mn for PBANT-AC and PBACT-AC films estimated from their AFM data.