EXCLUDED-VOLUME EFFECTS ON THE MEAN-SQUARE RADIUS OF GYRATION AND INTRINSIC-VISCOSITY OF ISOTACTIC OLIGO(METHYL METHACRYLATE)S AND POLY(METHYL METHACRYLATE)S

The mean-square radius of gyration and intrinsic viscosity were determ ined for isotactic poly(methyl methacrylate) (i-PMMA) with the fractio n of racemic diads f(r) similar or equal to 0.01 in acetone at 25.0 de grees C and in chloroform at 25.0 degrees C in the range of weight-ave rage molecular weight M(w) from 6.58 x 10(2) to 1.93 x 10(6). The resu lts for the gyration- and viscosity-radius expansion factors alpha(s) and alpha(eta) for i-PMMA along with those previously obtained for ata ctic poly(methyl methacrylate) (a-PMMA) with f(r) = 0.79 in the same s olvents are found to become functions only of the scaled excluded-volu me parameter (z) over tilde defined in the Yamakawa-Stockmayer-Shimada theory on the basis of the helical wormlike chain. Here, alpha(eta) f or i-PMMA has been calculated as before by taking account of the depen dence on solvent of the Flory-Fox factor Phi(0) in the unperturbed sta te. Thus the present results along with the previous ones for atactic polystyrene (a-PS), polyisobutylene, and a-PMMA lead to the conclusion that the quasi-two-parameter scheme is valid for alpha(s) and alpha(e ta) for a variety of polymer-solvent systems irrespective of the diffe rences in chain stiffness, local chain conformation, and solvent condi tion. This also indicates that there is no draining effect on alpha(et a) at least for these systems. It is found that the effects of chain s tiffness on alpha(s) and alpha(eta) remain appreciable even for M(w) > 10(6) for i-PMMA as well as for a-PS and a-PMMA. The effects are smal ler for i-PMMA than for a-PMMA both in acetone and in chloroform, refl ecting the fact that the former chain is less stiff than the latter. I t is also found that the values of the binary-cluster integral beta be tween beads (segments) for the two PMMAs in the same solvent are almos t identical with each other, indicating that beta is independent of th e stereochemical structure of the polymer chain.