EXCLUDED-VOLUME EFFECTS ON THE INTRINSIC-VISCOSITY OF OLIGOSTYRENE AND POLYSTYRENES - SOLVENT EFFECTS

The viscosity-radius expansion factor alpha(eta) of atactic polystyrene (a-PS) with the fraction of racemic diads f(r) = 0.59 was reinvestigated mainly in order to resolve a deviation of literature experimental data for alpha(eta)3 of a-PS in benzene at 25.0-degrees-C from a universal curve in the log alpha(eta)3 Vs log alpha(S)3 plot established for other polymer-solvent systems, where alpha(S) is the (gyration-)radius expansion factor. For this purpose, the intrinsic viscosity [eta] was determined for a-PS in benzene at 25.0-degrees-C, in methyl ethyl ketone (MEK) at 35.0-degrees-C, and in trans-decalin at 21.0-degrees-C (THETA) in the range of weight-average molecular weight M(w) from 5.78 X 10(2) to 3.84 x 10(6), and also the mean-square radius of gyration [S2] in these solvents in the range of M(w) from 3.59 x 10(5) to 3.84 x 10(6). The values of [eta] of oligostyrene samples in these three solvents, for which the excluded-volume effect was negligible, were confirmed to agree approximately with each other. The (double-logarithmic) plots of alpha(eta)3 against alpha(S)3 for a-PS in benzene at 25.0-degrees-C and in MEK at 35.0-degrees-C were found to follow the universal curve above, if the values of [eta]THETA and [S2]0 of a-PS in trans-decalin at THETA instead of those in cyclohexane at THETA are used as reference standards to calculate alpha(eta)3 and alpha(S)2, respectively. It was also found that the data for alpha(eta)3 of a-PS in various solvents form a single-composite curve when plotted against the scaled excluded-volume parameter z defined in the Yamakawa-Stockmayer-Shimada theory based on the helical wormlike chain model. Thus the present results confirm the previous conclusion that the quasi-two-parameter scheme may be regarded as valid for alpha(eta) as well as for alpha(S) irrespective of the differences in chain stiffness, local chain conformation, and solvent condition.