Equilibrium and Non-Equilibrium Phases and Phase Diagrams in Blends of Polymer Liquid Crystals with Enoineerino Polymers
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EQUILIBRIUM AND NON-EQUILIBRIUM PHASES AND PHASE DIAGRAMS INBLENDS OF POLYMER LIQUID CRYSTALS WITH ENOINEERINO POLYMERS WITOLD BROSTOW*, THEODORE S. DZIEMIANOWICZ
*,
MICHAEL HESS *' **
and ROBERT KOSFELD " * Center for Materials Characterization and Department of Chemistry, University of North Texas, Denton, TX 76203-5371 # Himont U.S.A., Inc., 800 Greenbank Road, Wilmington, DE 19808 FB6-Physikalische Chemie, Universitat Duisburg, Postfach 10 16 29, D-41 00 Duisburg 1, Federal Republic of Germany ABSTRACT This work represents a continuation of earlier studies of blends of polymer liquid crystals (PLC) with ordinary engineering polymers (EP). We now focus on connections between mechanical and other properties and phase structures and phase diagrams. Pure PLC are already two-phase systems; in each case addition of an EP complicates the situation further. In particular, we are concerned with phases which we call quasi-liquids, at temperatures between the glass transition and the melting point. Quasi-liquids do not have the mobility usually associated with liquids - because of the presence of other constituents and also because of orientational effects produced by the mesogenic groups. In phase diagrams of PLC-containing systems one should also take into account non-equlibrium phases. We are trying to show how such diagrams make possible Intelligent processing and a better control of properties of the PLC + EP materials. INTRODUCTION This paper represents a continuation of earlier work [1-41 aimed at mixing polymer liquid crystals (PLC) with ordinary engineering polymers (EP) In such a way that the valuable properties of PLC (reinforcement by mesogenic groups, stability at high temperatures, low isobaric expansivity, etc.) are preserved while costs are lower than that of pure PLC. However, in the present study we deal with variation of LC content in a series of PLC copolymers, while blends of one of these PLCs with an EP are dealt with In a companion paper [5]. While in earlier papers we used a variety of techniques and covered a wide range of properties, the present work Is focused on phase structures and phase diagrams. Reasons for this are stated In the following Section. Mat. Res. Soc. Symp. Proc. Vol. 171. ,e1990 Materials Research Society
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PHASE STRUCTURES, PHASE DIAGRAMS AND INTELLIGENT PROCESSING Properties of materials, polymeric or otherwise, are of course determined by chemical composition as well as by structures produced during processing. For PLCs the situation Is more difficult than for EPs; we know already from the first paper by Jackson and Kuhfuss (6] how easily acquire PLCs orientation during processing; high anisotropy of properties ensues. While in some cases the anisotropy is desirable, control of the resulting properties Is possible only if we have sufficcient knowledge of morphologies and phase structures, and also if we can locate each structure in the corresponding region in the phase diagram. While much Interesting and useful work on processing of PLCs and their blends has already b
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