Synthesis of liquid-crystalline comb-shaped copolymers and investigation of orientational elastic deformations in their nematic phase

Comb-shaped LC copolymers were synthesized by the free-radical copolymeriza tion of p-(6-acryloyloxycaproyloxyphenyl)-p'-methoxybenzoate and methyl acr ylate. The molar fraction of methyl acrylate was varied from 0 to 0.5 1. Th e temperatures of phase transitions were determined. The temperature depend ences of birefringence Delta n, order parameter S, and splay elastic consia nts K-1 of the resulting LC copolymers were estimated. The valueof the orde r parameter S depends on the composition of the copolymers only near a poin t corresponding to a nematic-isotropic melt transition the order parameter S decreases as the fraction of a nonmesogenic component increases. For the copolymers under study, the general temperature dependence of the order par ameter S of the copolymers was obtained in the region of relative temperatu res tau <0.96. The value of the splay elastic constant K-1 is virtually ind ependent of the composition of the copolymcrs. The data obtained are compar ed with the corresponding characteristics of linear thermotropic polymers.