ON THE UNIVERSAL CONSTANTS RHO AND PHI OF FLEXIBLE POLYMERS

The translational diffusion coefficient D, intrinsic viscosity [eta], and mean-square radius of gyration <S2> were determined for several high molecular weight samples of atactic polystyrene in cyclohexane at 34.5-degrees-C and in trans-decalin at 21.0-degrees-C, of atactic poly(methyl methacrylate) (a-PMMA) in acetonitrile at 44.0-degrees-C and in n-butyl chloride at 40.8-degrees-C, of polyisobutylene in isoamyl isovalerate at 25.0-degrees-C, and of poly(dimethylsiloxane) (PDMS) in bromocyclohexane at 29.5-degrees-C, all these temperatures being the respective THETA-temperatures. With the data obtained, the ratio-rho of <S2>1/2 to the hydrodynamic radius defined from D and the ratio (Flory-Fox factor) PHI of the hydrodynamic volume defined from [eta] to <S2>3/2 were calculated. The results are the following. For PDMS, rho rho- decreases and PHI-increases with increasing weight-average molecular weight M(W) in the range of such large M(W) that <S2>/M(W) is independent of M(W), indicating that the so-called "draining effect" exists. For the other polymers, rho and PHI are independent of M(W) in such a range of M(W), as was expected. However, their values (with polydispersity corrections), including the asymptotic values for PDMS, seem rather universal within experimental error except for a-PMMA in acetonitrile. A detailed theoretical discussion of the results is also given.