Radius of Gyration of Polystyrene Combs and Centipedes in a ϑ Solvent

The molecular weight dependence of the radii of gyration R g in a ϑ solvent ( trans -decalin) of one regular branched comb and three regular centipede polystyrenes was studied using a gel permeation chromatography system equipped with a two-angle light scattering detector and a refractive index detector. R g in trans -decalin for each sample of particular molecular weight was about 25% smaller than that in a good solvent (tetrahydrofuran, THF). On the other hand, they are 20−40% larger than the theoretical values from the Gaussian chain model. This difference can be explained with the wormlike comb model developed by Nakamura et al. ( Macromolecules 2000, 33, 8323−8328). Persistence lengths thus obtained for each sample were about half of that determined in THF solution. However, they are significantly larger than that for linear polystyrene. These results suggest that a main chain stiffening effect exists in comb polystyrenes even in a ϑ solvent.