Positron Annihilation Lifetime Spectroscopy for Miscibility Investigations of Styrene-Butadiene-Styrene Copolymer/Polystyrene Blends

摘要

The free volume parameters of styrene-butadiene-sty-rene copolymer/polystyrene (SBS/PS) blends were investigated with positron annihilation lifetime spectroscopy (PALS) in this study. The behaviors of free volume distribution, average free volume, and relative fractional free volume revealed the difference of inter-facial miscibility. Based on different models, inter-chain interaction parameter p, geometric factor γ, and hydro-dynamic interaction parameter a obtained from free volume data were employed to further determine the effect of molecular architecture and styrene content on the miscibility. The results suggest the better miscibility in star-shaped SBS/PS blends than that of corresponding linear SBS/PS systems, even than that of systems containing more styrene unit. In addition, differential scanning calorimetry, dynamic mechanical analysis, and scanning electron microscopy, which are sensitive to heterogeneities in larger domain size, give different results of miscibility from free volume data. It should be attributed the difference of characterization scale. The mechanical property corroborates the results of miscibility.