Mutual diffusion and thermodynamics in the blends of polystyrene and tetramethylbisphenol‐A polycarbonate

A study was made of miscible polymer blends of deuterated polystyrene (d‐PS) and tetramethylbisphenol‐A polycarbonate (TMPC). The Flory interaction parameter χ was obtained from the relation between mutual and tracer diffusion coefficients, D̃ and D * , which were measured by forward recoil spectrometry. The temperature dependence of diffusion at PS weight fractions ω of 0.25 and 0.5, and the composition dependence at temperatures 45°C above the glass transition temperature, T g , were investigated. A stronger dependence of χ on both temperature (at ω = 0.5) and composition was observed in comparison with other miscible binary polymer blends involving PS. Analysis using the generalized lattice‐fluid model of Sanchez and Balazs 1 showed that the incorporation of a significant specific interaction is needed to explain the temperature dependence of χ. The diffusion coefficients obtained in the one‐phase region were extrapolated to the two‐phase region, and these were compared with the effective diffusion coefficient extracted from phase separation dynamics measured by light scattering. 2 A significant discrepancy between the extrapolated and effective diffusion coefficients was observed.