Femtosecond relaxation dynamics in dialkoxy-substituted poly-(p-phenylenevinylene) derivatives

We investigated the sub-picosecond relaxation dynamics of two alkoxy-substitued poly-p-phenylenevinylenes that differ only for the structure of the alkoxy side chains. Photoinduced absorption, bleaching, and stimulated emission were observed in distinct spectral regions. Our results show that the temporal dynamics of stimulated emission strongly depends on excitation density. We ascribe such behavior to on-chain ultrafast nonlinear processes, which are almost independent on the substituents grafted onto the polymeric backbone.