PREPARATION AND PHYSICAL-PROPERTIES OF POLYURETHANE ELASTOMERS CONTAINING MESOGENIC MOIETIES

The mesogenic diols containing azobenzene, benzophenone and biphenyl m oieties with an alkoxy flexible spacer were synthesized, and the linea r polyurethanes were prepared by the polyaddition of these diols with diisocyanates such as 2,4-toluene diisocyanate and 4,4'-diphenylmethan e diisocyanate. From the measurement of DSC and polarizing optical mic roscopy with the hot stage, it was found that most resulting polyureth anes revealed a thermotropic liquid crystalline behaviour and the temp erature of mesomorphic phase was effected significantly by the molecul ar structure of diisocyanates and the chain length of flexible spacers . On the other hand, the segmented polyurethanes were prepared by the chain extension of isocyanate-terminated prepolymers with these mesoge nic diols. As the results, it was found that the incorporation of meso genic moieties to the hard segment of the polyurethanes contributed to the enhancement of thermal stability and mechanical properties.