EXCLUDED-VOLUME EFFECTS ON THE INTRINSIC-VISCOSITY OF OLIGOMERS AND POLYMERS OF STYRENE AND ISOBUTYLENE

The intrinsic viscosity [eta] was determined for atactic polystyrene (a-PS) in toluene at 15.0-degrees-C in the range of weight-average molecular weight M(w) from 2.66 x 10(2) to 3.84 x 10(6) and for polyisobutylene (PIB) in n-heptane at 25.0-degrees-C in the range of M(w) from 1.12 X 10(2) to 1.76 x 10(6). These solvents and temperatures have been chosen so that the values of [eta] for the unperturbed a-PS and PIB chains in given good solvents may coincide with the respective values of [eta]0 in cyclohexane at 34.5-degrees-C (THETA) and in isoamyl isovalerate at 25.0-degrees-C (THETA). It is then found that the viscosity-radius expansion factor alpha(eta) thus determined correctly is a function only of the radius expansion factor alpha(S) in a first approximation, in contrast to literature data. When plotted against the conventional excluded-volume parameter z, the present data for alpha(eta) do not form a single-composite curve as yet, depending on the chain stiffness. However, the data form such a curve when plotted against the scaled excluded-volume parameter z defined in the Yamakawa-Stockmayer-Shimada theory for the wormlike and helical wormlike chains with excluded volume. Thus a quasi-two-parameter scheme may be regarded as valid for alpha(eta) as well as for alpha(S). It is also pointed out that the relation between alpha(eta) and z (or z) is still worth deriving theoretically.