Photoinduced Orientation of Azobenzene Chromophores in Amorphous Polymers As Studied by Real-Time Visible and FTIR Spectroscopies

Abstract

In situ dynamical study of the photoinduced orientation of the DR1 azobenzene derivative in a doped PMMA matrix and in p(DR1A-co-MMA) copolymers was carried out using real-time visible and infrared spectroscopies. The different mechanisms occurring during the photoisomerization cycles were highlighted by following the time dependence of the normalized average absorbance (T0), the normalized linear dichroism (T2) and the order parameter (P2) 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 T0 and T2 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 various samples. On one hand, the chromophore−matrix interactions were investigated in doped systems by changing the tacticity of the PMMA matrix. On the other hand, the chromophore−chromophore interactions in functionalized polymers were studied by changing the concentration of azobenzene units in copolymer systems.