The approach of deriving new photooptically active polymeric substances by hydrogen bonding between functionalized liquid crystalline (LC) copolymers and low-molecular-mass dopants, containing photochromic azobenzene fragments, is described. The formation of intermolecular hydrogen bonds between carboxylic groups of functionalized LC copolymers and the pyridine fragment of the dopant leads to stable, nonseparating mixtures in a broad interval of contents (up to 30 mol % dopant molecules). The phase behavior and structure of photochromic mixtures are investigated. Induction of a nematic mesophase is observed in the case of a smectic polymer matrix doped with low-molar-mass photochromic dyes.

Photochromism has been studied for two comb-like liquid-crystalline copolymers (I) and (II) containing azobenzene chromophores in their side chains. In a smectic glass phase of both copolymers, upon short-time irradiation by UV light, long-living cis isomers are observed. Both copolymers manifest the photoinduced anisotropy, the physical mechanisms of which seem to be quite different. In spin-coated films of polymer (II), the origin of the anisotropy is a strong stable dichroism, which is due to an enrichment and depletion of the chosen angular direction, correspondingly, with trans and cis isomers of the azobenzene chromophores. Polymer (I) manifests no dichroism at all, and its induced optical anisotropy may be accounted for by a rather slow chromophore reorientation. In copolymer (II) a considerable reorientation of the mesogenic groups also occurs as a secondary phenomenon at the stage of the cis isomer formation only. This observation shed more light on the general process of the light-induced molecular reorientation in polymers, liquid crystals, and Langmuir–Blodgett films, which is of great importance for holographic information recording.

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