Liquid-Crystal Polymer

(LC polymer, liquid-crystalline polymer, mesomorphic polymer) A polymer capable of forming regions of highly ordered structure (mesophase) while in the liquid (melt or solution) phase. The degree of order is somewhat less than that of a regular solid crystal. Four types have been identified: rodlike, including aromatic polyamides, esters, azomethines, and benzobisoxazoles; helical, mostly natural materials such as polypeptides; side-chain (comb polymers); and block copolymers with alternating rigid and flexible units. These polymers are described as nematic, in which the mesogens (ordered regions) show no positional order, only long-range order; Cholesteric or chiral, a modified nematic phase in which the orientation direction changes from layer to layer in a helical pattern; and smectic, in which the mesogens have both long-range order and 1- or 2-dimensional positional order. Liquid-crystal polymers are difficult to get into the molten condition because the solid crystals generally...