Glass-formation kinetics of miscible blends of atactic polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide)

We present a detailed investigation of the kinetics associated with the gla ss transitions of miscible blends composed of atactic polystyrene (a-PS) an d poly(2,6-dimethyl-1,4-phenylene oxide) (PPO). According to both dynamic m echanical analysis and differential scanning calorimetry, relaxation times displayed an enhanced temperature dependence (i.e., more fragile or more co operative behavior) for the blends compared with additive behavior based on the responses of neat a-PS and PPO. This is consistent with the notion tha t specific interactions between the blend components heighten the intermole cular cooperativity. The compositional dependence of fragility provided ins ight into physical aging results for the properties of volume and enthalpy. The combination of our research and a previously reported pressure-volume- temperature study by Zoller and Hoehn (J Polym Sci Polym. Phys Ed 1982, 20, 1385) provided evidence that the observation of increased glassy densities for the blends compared with those of the pure polymers was kinetic in ori gin and was not a feature of the thermodynamics of miscibility. (C) 2001 Jo hn Wiley & Sons, Inc.