Modified Azo-Polysiloxanes for complex Photo-Sensible supramolecular systems

Abstract

Here we show the possibility to obtain different types of azo-polysiloxanes capable to respond to light stimuli. The azo-polymers were prepared starting from a polysiloxane containing chlorobenzyl groups in the side-chain, using a twostep substitution reaction. In the fi rst step, the polysiloxanes were modifi ed with azo-benzene groups and, in the second one, different systems, as functions of the envisaged application (nucleobases, donor/acceptor or ammonium quaternary groups) were connected to the side-chain. The photochromic behavior in the presence of UV irradiation or natural visible light was investigated, in solution or in the solid state. Even the maximum conversion degree from trans- To cis- confi guration of the azo groups is slightly lower in the solid state as compared with the solution, the response rates are similar on the time-scale. The cis-trans relaxation behavior is different for the systems containing nucleobases, as compared with the donor/acceptor ones. In the case of the azo-polysiloxanes containing quaternary ammonium groups, the polymer aggregation capacity was investigated. The critical aggregation concentration is situated at lower values that can be explained by the azobenzenic group aggregation capacity to generate a hydrophobic micelle core. © 2008 Springer Science+Business Media B.V.