Theory of microphase separation on Side-Chain Liquid-Crystalline Polymers with flexible spacers

摘要

We model a melt of monodisperse side-chain liquid crystalline polymers as amelt of comb copolymers in which the side groups are rod-coil diblockcopolymers. We consider both excluded volume and Maier-Saupe interactions. Thefirst acts among any pair of segments while the latter acts only between rods.Using a free energy functional calculated from this microscopic model, we studythe spinodal stability of the isotropic phase against density and orientationalfluctuations. The phase diagram obtained in this way predicts nematic andsmectic instabilities as well as the existence of microphases or phases withmodulated wave vector but without nematic ordering. Such microphases are theresult of the competition between the incompatibility among the blocks and theconnectivity constrains imposed by the spacer and the backbone. Also theeffects of the polymerization degree and structural conformation of themonomeric units on the phase behavior of the side-chain liquid crystallinepolymers are studied.