COMB-SHAPED LIQUID-CRYSTALLINE IONOGENIC COPOLYMERS

A series of new ionogenic liquid crystalline (LC) copolymers (A4CB-AA) was prepared by radical copolymerization of 4-(4-cyanobiphenyl-4'-ylo xy) butyl acrylate (A4CB) and acrylic acid (AA). The presence of the A A units do not prevent the development of the nematic phase, which is typical of the initial cyanobiphenyl homopolymer. At a content of AA o f 42-52 mol%, the copolymers produce the S-Ad type of mesophase, and t his phenomenon is explained by an increased rigidity of the main chain due to the development of intramolecular hydrogen bonds. By increasin g the concentration of AA units higher than 55 mol%, the development o f mesophase is prevented, and the as-received copolymers are amorphous . A crucial role of intramolecular hydrogen bonds for the development of the SA phase in the copolymers is proved by synthesizing and studyi ng the copolymers, in which the same type of the mesogenic group A4CB is preserved but the second component is provided by methyl ether of a crylic acid; such copolymers are able to produce only a nematic phase. Studying orientation of LC A4CB-AA copolymers in the magnetic field b y the method of wide-line H-1 NMR spectroscopy allows one to calculate the temperature dependences of order parameter S and to advance a cor rect interpretation of experimental data.