ON THE PHASE-BEHAVIOR OF BLENDS OF POLYMERS AND NEMATIC LIQUID-CRYSTALS

The phase behavior of mixtures of polymers and nematic liquid crystals (LC) is investigated. Two types of systems are examined. The first on e deals with blends in which the polymer is made of Linear chains. In this case, a systematic study of the effects of various parameters on the phase diagrams is performed. In particular, it is shown how increa sing the polymer size and/or the LC molecule size increases the miscib ility gap of the mixture. It also reduces the region where a single ne matic phase is observed in the presence of a tiny amount of polymer. L ikewise, the relative effects of the isotropic and the nematic interac tion parameters on the phase diagrams are examined. The second part of this investigation deals with blends involving crosslinked polymers. Here, substantial differences are observed as compared to the case whe re the polymer components are made of linear chains. These differences are illustrated by showing the phase diagrams in similar conditions f or both blends. Unlike the case of a Linear polymer matrix, it is obse rved that the single nematic phase and the nematic-isotropic spinodal branches are absent from the phase diagram of crosslinked polymers. Th is results into significant distortions of the phase diagram. In order to highlight all these effects, examples representing hypothetical bl ends are considered. These examples are chosen for illustration of the results in which the choice of numerical parameters is made consisten tly with the existing values in the literature which makes comparison with published data possible.