DYNAMIC-MECHANICAL BEHAVIOR OF HYBRID THERMOTROPIC LIQUID-CRYSTALLINEBLOCK-COPOLYMERS

The preparation and the dynamic-mechanical behavior of a novel class o f liquid crystalline block copolymers is described. In a first step, h ydroxyl terminated oligoesters were obtained by polycondensation react ion of methylhydroquinone and 4,4'-dicarboxy-1,10-dibenzoyloxydecane i n pyridine solution in the presence of tosyl chloride and dimethylform amide. Hydroxyl terminated oligoesters were then further polymerized w ith 4,4'-azo-bis(4-cyanopentanoyl chloride) and, in a third step, the macroinitiators obtained were employed in the free-radical polymerizat ion of styrene. The DMA analysis showed that the two different blocks were only partly compatible in the glassy and melt phases and underwen t distinct phase transitions. The nematic-isotropic transition tempera ture of the polyester block was constant throughout the whole composit ion range and the phase transition enthalpy was directly proportional to the percent of the polyester block.