Molecular engineering of liquid-crystalline polymers by living polymerization. Part 20.—Synthesis and characterization of binary copolymers of [11-(4′-cyanobiphenyl-4-yloxy)undecanyloxy]ethylene with n-butyl vinyl ether, and of 2-[(4′-cyanobiphenyl-4-yl)oxy]ethyl vinyl ether with (n-butoxy)ethylene

Abstract

The synthesis and characterization of poly{1-[11-(4′-cyanobiphenyl-4-yloxy)undecanyloxy]ethylene-co-1-(n-butoxy)ethylene}X/Y{poly[(6-11)-co-(BVE)]X/Y}(where X/Y represents the molar ratio of the two structural units) and poly{1-[2-(4′-cyanobiphenyl-4-yloxy)ethoxy]ethylene-co-1-(n-butoxy)ethylene}X/Y{poly[(6-2)-co-(BVE)]X/Y} with degrees of polymerization of ca. 20 and molecular-weight distributions of ca. 1.10 are described. The mesomorphic behaviour of all copolymers determined from differential scanning calorimetric (DSC) and thermal optical polarized microscopy measurements is discussed as a function of copolymer composition. Poly(6-11) exhibits enantiotropic S_A and S_x mesophases, while poly(6-2) is only glassy. Poly[(6-11)-co-(BVE)]X/Y with X/Y from 2/8 to 10/0 exhibit an S_A phase. Both the temperature transitions and the enthalpy changes associated with this S_A phase display continuous and linear dependences of copolymer composition. Poly[(6-2)-co-(BVE)]X/Y with X/Y from 10/0 to 6/4 exhibit an induced monotropic nematic mesophase.