Molecular weight dependence of the intrinsic viscosity of polymer solutions. II

TLDR: In this paper, the intrinsic viscosities of polystyrene and polyisobutylene fractions in good and in ideal solvents were examined from the point of view of their dependence on molecular weight.

Abstract: Intrinsic viscosities of polystyrene and polyisobutylene fractions in good and in “ideal” solvents have been examined from the point of view of their dependence on molecular weight. A compilation of results is presented which covers exceptionally wide ranges, from several thousand to several to million, in molecular weight. The intrinsic viscosity in an “ideal” solvent (i.e., cyclohexane at 34°C. for polystyrene, or benzene at 24° for polyisobutylene) is remarkably well fitted over the molecular weight range cited above by the relation: where K is a constant, independent of molecular weight, for a particular polymer at a given temperature. The molecular expansion factor α3 which applies in good solvents (e.g., toluene for polystyrene and cyclohexane and diisobutylene for polyisobutylene) as calculated from: increases with molecular weight approximately in accordance with the relationship: However, the quantity (α5 − α3)/M1/2 changes appreciably with M in some cases. This is particularly true for molecular weights below 50,000. Results of an examination of the effect of rate of shear on the viscosity of polystyrene in benzene at 25° and in cyclohexane at 34°, and of the intrinsic viscosity-molecular weight relation for polystyrene in benzene at 25°, are reported.