PHOTOINDUCED ORIENTATION OF AZOBENZENE CHROMOPHORES IN AMORPHOUS POLYMERS AS STUDIED BY REAL-TIME VISIBLE AND FTIR SPECTROSCOPIES

In situ dynamical study of the photoinduced orientation of the DR1 azo benzene derivative in a doped PMMA matrix and in p(DR1A-co-MMA) copoly mers was carried out using real-time visible and infrared spectroscopi es. The different mechanisms occurring during the photoisomerization c ycles were highlighted by following the time dependence of the normali zed average absorbance (T-0), the normalized linear dichroism (T-2) an d the order parameter (P-2) during the orientation (laser on) and the relaxation (laser off) periods. The thermal cis-trans back-relaxation and the angular redistribution were followed separately from the T-0 a nd T-2 relaxation curves, respectively. The orientation and relaxation curves were fitted by the Kohlrausch-Williams-Watts (KWW) function in order to compare the rate constant and the distribution width for var ious samples. On one hand, the chromophore-matrix interactions were in vestigated in doped systems by changing the tacticity of the PMMA matr ix. On the other hand, the chromophore-chromophore interactions in fun ctionalized polymers were studied by changing the concentration of azo benzene units in copolymer systems.