Second Virial Coefficients and Radii of Gyration for Poly(α-methylstyrene) in Cyclohexane below the ϑ Temperature

Classical and low-angle laser light-scattering experiments were performed to measure the second virial coefficient, A 2, and radius of gyration, R g, of linear poly(α-methylstyrene) (PαMS) in the poor solvent cyclohexane. The molecular weights, M w, of the polymers used cover the range of 60 000−3 500 000, and all samples have narrow molecular weight distributions. The experimental temperatures are controlled down to about 16 °C below the ϑ temperature (36.2 °C). At this temperature, the scaling exponent of R g with M w is 0.414; this appears to be the lowest exponent ever reported for linear chains of synthetic polymers in solution. A strong molecular weight dependence of the measured A 2 values for this PαMS/cyclohexane system is observed. These results are compared with the predictions of available theories and with other experimental results.