Design and electro-optic behavior of novel polymer-liquid crystalline composites

The novel stable liquid crystals (LC) dispersed polymers have been developed. The first of them is based on the LC mixture consisting of 4-methoxybenzylidene-4'-butylaniline and 4-ethoxybenzylidene-4'-butylaniline with molar ratio of 1:1 (H37) and poly (2-methyl-5-vynilpyridine) (PMVP). The second consists of the LC 4-pentylcyano-4'-biphenyl (5CB) and poly (ethylene glycol) (PEG). The mesogenic substance 4-n-heptyoxibenzoic acid (HOBA) is served for stabilization of obtaining composites. Kinetics of network formation is investigated by methods of polarization microscopy and integrated small-angle scattering. It is shown that gel-like states of the composite H37 + PMVP + HOBA and 5CB + PEG + HOBA are formed at polymer concentration above 7 wt.% and 9 wt.%, correspondingly. At slow cooling, the system separates into a liquid crystal-rich phase and a liquid crystal-poor phase. At this case, transition of these phases in the H37 + PMVP + HOBA (87 wt.% + 12 wt.% + 1 wt.%) composite to an anisotropic state occurs at 49.2 degrees C and 41.4 degrees C, accordingly, while the composite 5CB + PEG + HOBA (85 wt% + 13 wt.% + 2 wt.%) passes to an anisotropic state at temperature 35.5 degrees C corresponding to the isotropic-nematic transition of pure 5CB. The basic electro-optic parameters of the obtained composites are determined at room temperature. Experimental results are explained by phase separation of the system, diminution of a working area of electro-optical effects and influence of areas with the high polymer concentration on areas with their low concentration. (C) 2016 Elsevier B.V. All rights reserved.