Excluded-Volume Effects in Star Polymer Solutions: Six-Arm Star Polystyrene in Cyclohexane near the ϑ Temperature

Abstract

Anionically polymerized six-arm star polystyrene samples with weight-average molecular weights Mw of 5.6 × 104−3.2 × 106 were studied by light scattering and viscometry in cyclohexane at different temperatures to determine their z-average mean-square radii of gyration (〈S2〉z), second and third virial coefficients (A2 and A3), and intrinsic viscosities ([η]). The values of A3 at the ϑ point (34.5 °C), where those of A2 were essentially zero for Mw > 106, were about 5 × 10-4 cm6 mol g-3 and yielded 4 × 10-45 cm6 for the ternary cluster integral. The data for 〈S2〉z and A2 at ϑ were in line with previous perturbation calculations taking into account ternary cluster interactions, but the (residual) ternary effects on these properties were not very significant, at least, for Mw > 106. The expansion factor αS2 for 〈S2〉 and that for [η] plotted against the conventional excluded-volume parameter for Mw > 1 × 106 came close to the known relations for both linear and four-arm star polystyrenes of high molecular weig...