T. Sterzynski, D. Guigner, W. Brostow, and M. Plass

Departments of Materials Science and Chemistry, University of North Texas, Denton, TX 76203-5310, USA

ABSTRACT

Blends of thermoplastic engineering polymers (EPs) with polymer liquid crystals (PLCs) can show properties close to those of PLCs but at affordable prices.  While several EP + PLC blend pairs have been reported in the literature, there is a need for more, and for those in which the blend properties do indeed approach those of pure PLCs.  We have studied blends of poly(vinylidene fluoride) (PVDF) containing 5, 10, 15 and 20 weight% of a longitudinal PLC, namely PET/xPHB, where PET is poly(ethylene terephthalate), PHB is p-hydroxybenzoic acid, and x is the mole fraction of the LC component (here PHB) in the copolymer. For all compositions, a significant drop in viscosity with respect to pure PVDF is observed.  We are observing the channelling effect predicted theoretically by our extension of the statistical-mechanical theory of Flory [25]:  the rigid PLC sequences in the PLC chains cause orientations not only of those entire chains but also of the neighboring PVDF chains. The crystallization of PVDF is clearly affected by the presence of the PLC. The nucleation effect causes an increase in crystallization temperature of PVDF.  At the same time, we observe a decrease in the PVDF crystallization rate, clearly caused by the perturbation of the structure of the thermoplastic matrix by the PLC chains. Optical microscopy, wide angle X-ray scattering and Raman spectroscopy all confirm the existence of orientation not only of the spherulites but also of the PLC chains in the PVDF matrix. Copyright 1998 /Science Ltd. All rights reserved.