ORIENTATIONAL CHANGES INDUCED BY AXIAL STRESS IN A HIGHLY ALIGNED LIQUID-CRYSTALLINE COPOLYESTER

The non-linear mechanical behaviour exhibited by oriented thermotropic liquid crystalline polymers has been attributed to an increase in mol ecular orientation caused by the applied tensile stress. In this work we have detected the postulated change in orientation by polarized inf ra-red spectroscopy. It is shown that there is reasonable quantitative agreement between the infra-red measurement of change in molecular or ientation and the change predicted by modelling the change in tensile modulus with stress.