Synthesis and Photoresponsive Functionality of Azomethine and Azo-Azomethine Polymers

Fluorinated poly(arylene ether)s (FPAEs) incorporating azomethine linkages and combined azo-azomethine chromophores were synthesized and investigated. The photoresponsive properties of the obtained polymers were examined in both solution and thin films. The comparative analysis of photoisomerization kinetics indicates that the FPAEs with azo-azomethine groups follow the first-order trans–cis photoisomerization kinetics. In contrast, nonlinear trans–cis behavior of azobenzene– N -salicylideneaniline polymers (with the OH group in the ortho position relative to the azomethine group) is primarily governed by stabilizing backbone hydrogen bonds and, to some extent, by excited-state intramolecular proton transfer process. The purely azomethine-based polymer showed no detectable photoisomerization under the studied conditions. Thin films of azo-azomethine copolymers exhibited controllable response with stable photoinduced birefringence enabling efficient fabrication of diffraction gratings as well as mask-assisted photopatterning, producing well-defined photoalignment layers for nematic liquid crystals. The effectiveness of the photoaligned polymer surfaces was evaluated by measurements of the azimuthal anchoring energy at the liquid crystal interface.