INFLUENCES OF SUBSTRATES SURFACES ON THE BAND FORMATION BEHAVIOR IN AN ORIENTED THERMOTROPIC LIQUID-CRYSTALLINE POLYESTER

The influences of substrate surfaces on the formation behaviour of ban ded texture and its thermal stabilities have been studied for an aroma tic X-shaped main-chain liquid crystalline polyester. The oriented pol ymer films prepared by shear on a glass substrate were found to exhibi t a strong bounding effect, which was very effective in stabilizing or keeping the structural orders of oriented polymer chains, even for a long time in the mesomorphic state and also in stimulating the band fo rmation process during cooling. Such an influence is considered to ari se from strong interfacial interactions between the solid substrate an d the mesomorphic polymer molecules deposited on it. Similar phenomena were also observed in the case of PET him adopted as substrate. Howev er, they were quite different when the glass substrate was replaced by a Teflon sheet: the uniformity of polymer chain alignments on it was difficult to maintain even in a rapid cooling process after shear cess ation, resulting in a formation of irregular banded texture. The melti ng-induced re-orientation behaviour of polymer chains was also examine d for a drawn fibre. Copyright (C) 1996 Elsevier Science Ltd.