Smart Ionic Sol−Gel-Based Azobenzene Materials for Optical Generation of Microstructures

We propose a concept of supramolecular materials for effective all-optical generation of surface relief structures. The materials are based on the ionic interactions between oppositely charged photochromic azobenzene units and polysiloxane backbones formed in situ. The materials are easy to produce from commercial components. Using ionic interactions to connect photochromic units to the polymer backbones allowed very high dye-doping levels without aggregation. Because of this noncovalent bonding the polymer chains got involved in the photoinduced translation motion of azobenzene units resulting in very effective formation of surface relief gratings. For the first time some relaxation processes which counteract the light-induced formation of surface relief structures were suggested. Under consideration of these processes the influence of network formation and alternatively of glassy state on the efficiency of mass transport and the stability of induced structures was discussed. Because of the simplicity and versatility of the concept the new family of materials for applications in optics, sensorics, and biology may be designed.