Phase behavior and rheology of blends containing polycarbonate and a thermotropic polyester

Abstract

The phase behavior and rheology of binary blends of polycarbonate (PC) and a liquid crystalline polymer (LCP) have been investigated. The thermotropic LCP employed was a semiflexible polyester synthesized by melt condensation of t-butylhydroquinone and 4,4′ dichloroformyl-α,ω-diphenoxyhexane. It shows a distinct nematic-to-isotropic transition in the pure state and in the blends. Results of DSC and optical microscopy indicate that the LCP is solubilized in the mixture for weight fractions of LCP less than about 0.05 and shows partial miscibility with PC over the rest of the composition range. The phase separation is considered to be driven by both isotropic and anisotropic interactions between constituent chains. Dynamic oscillatory measurements show that there is some interaction between the separate isotropic and anisotropic phases, with complex viscosities of the blends being intermediate between those of pure components and showing significant deviation from a logarithmic rule-of-mixtures. © 1996 John Wiley & Sons, Inc.