Second Virial Coefficient of Oligo- and Poly(α-methylstyrene)s. Effects of Chain Stiffness, Chain Ends, and Three-Segment Interactions

Abstract

The second virial coefficient A2 was determined from light scattering measurements for atactic oligo- and poly(α-methylstyrene)s (a-PαMS) with the fraction of racemic diads fr = 0.72 over a wide range of weight-average molecular weight Mw from 6.48 × 102 to 5.46 × 106 in cyclohexane at 30.5 °C (ϑ) and in toluene at 25.0 °C, and for Mw ≥ 2 × 105 in 4-tert-butyltoluene at 25.0 °C, in n-butyl chloride at 25.0 °C, and in cyclohexane at 35.0, 45.0, and 55.0 °C. It is shown that the observed characteristic features of A2 at ϑ, which is denoted by A2,ϑ, as a function of Mw in cyclohexane at ϑ, i.e., a sharp increase with decreasing Mw for small Mw and a rather long-tailed negative region for large Mw, may be well explained by the theory that takes account of the effects of chain ends and also of three-segment interactions. It is also shown that the observed dependence of A2 on Mw in toluene may be quantitatively explained by the theory that takes account of the effects of chain stiffness, local chain conformatio...