MAIN-CHAIN LYOTROPIC LIQUID-CRYSTALLINE ELASTOMERS .1. SYNTHESES OF CROSS-LINKED POLYISOCYANATE GELS ACQUIRING LIQUID-CRYSTALLINE BEHAVIOR IN THE SWOLLEN STATE

Copolymers of n-hexyl and allyl isocyanates were successfully synthesi zed using an organotitanium(IV) catalyst initiated polymerization. Vis cosity measurements indicated that molecular weight increased with dec rease in monomer/initiator ratio. Monomer reactivity ratios were calcu lated using the copolymer composition equation, and the resulting valu es indicated relative randomness in the copolymer. The liquid-crystall ine behavior of these copolymers was studied with regard to their mole cular weight, composition, and concentration. Radical cross-linking wa s extensively studied but yielded only very brittle gels. Consequently , hydrosilation cross-linking was investigated and did yield networks suitable for orientation in a novel technique for increasing the mecha nical properties of polymer films. All the hydrosilation cross-linked gels exhibited brilliant mesomorphic birefringence under a cross-polar ized microscope at low cross-link density. In addition, the glass tran sition temperatures of the hydrosilation cross-linked networks were fo und to be lower than those of their constituent polymers.