Polymacromonomer consisting of polystyrene. Light scattering characterization in cyclohexane

Nine samples of a polymacromonomer consisting of polystyrene with a fixed s ide-chain length of 33 styrene residues and ranging in total weight-average molecular weight M-w from 1.9 x 10(5) to 1.1 x 10(7) have been prepared an d studied by light scattering in cyclohexane at temperatures between 25 and 45 degrees C. The second virial coefficient is found to vanish at 34.5 (+/ -2)degrees, the Theta temperature for linear polystyrene in cyclohexane. Th e M-w dependence of z-average mean-square radius of gyration [S-2](z) at th is temperature is analyzed on the basis of the wormlike chain to obtain 22n m for Kuhn's statistical segment length lambda(-1) and 13000 nm(-1) for the molar mass per unit contour length. The chain stiffness as indicated by th is lambda(-1) value is one order of magnitude higher than that of linear po lystyrene. Analysis of [S-2](z) at temperatures other than the Theta point is also made with the aid of the quasi-two-parameter theory for excluded-vo lume effects. It is found that lambda(-1) increases gradually with raising temperature or increasing excluded-volume strength.