Investigations on photoinduced processes in a series of azobenzene-containing side-chain polymers

We present a spectrophotometric investigation of the processes in three azobenzene polymers induced by a linearly polarized Ar beam (488 nm). The polymers differ only in the length of the spacers attaching the chromophores to the main chain. The experimental results show that this difference determines not only the polymer structure; it also substantially influences the value of the photoinduced dichroism and its time behaviour after the illumination. We explain this on the basis of the different efficiencies of the two main photoinduced processes in the azobenzenes-the selective trans-cis isomerization and the reorientation of the trans-azobenzenes. The results from a real-time measurement of the photoinduced anisotropic changes in the refractive indices of the three polymers support this understanding.