Polymacromonomer consisting of polystyrene. Light scattering characterization in cyclohexane

Abstract

Nine samples of a polymacromonomer consisting of polystyrene with a fixed side-chain length of 33 styrene residues and ranging in total weight-average molecular weight Mw from 1.9 × 105 to 1.1 × 107 have been prepared and studied by light scattering in cyclohexane at temperatures between 25 and 45°C. The second virial coefficient is found to vanish at 34.5 (± 2)°C, the Θ temperature for linear polystyrene in cyclohexane. The Mw dependence of z-average mean-square radius of gyration 〈S2〉z at this temperature is analyzed on the basis of the wormlike chain to obtain 22 nm for Kuhn's statistical segment length λ-1 and 13000 nm-1 for the molar mass per unit contour length. The chain stiffness as indicated by this λ-1 value is one order of magnitude higher than that of linear polystyrene. Analysis of 〈S2〉2 at temperatures other than the Θ point is also made with the aid of the quasi-two-parameter theory for excluded-volume effects. It is found that λ-1 increases gradually with raising temperature or increasing excluded-volume strength.