Induction of the cholesteric mesophase in hydrogen-bonded blends of polymers with a low molecular mass chiral dopant

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Abstract
A family of new hydrogen bonded complexes based on comb-shaped LC copolymers containing alkyloxy-4-oxybenzoic acid mesogenic fragments and chiral dopant molecules, derivatives of pyridine-4-carboxylic acid has been prepared. At concentrations of chiral groups in the range 1-25 mol%, induction of the cholesteric phase is observed. The temperature dependences of the selective light reflection wavelength were studied, and the helix twisting power was calculated. Depending on the type of polymer nematic matrix, this value varies in the range 12.1 to 18.3mum 1. With respect to optical properties, the chiral nematic phase in the hydrogen-bonded complexes is comparable to that in classical cholesteric copolymers in which the chiral group is covalently bound to the polymer chain.