CHAIN AND SPHERE DIFFUSION IN POLYISOBUTYLENE-CHCL3 - A REANALYSIS

Previously reported (Brown, W.; Zhou, P. Macromolecules 1989, 22,4031; Zhou, P.; Brown, W. Macromolecules 1989, 22, 890) experimental studies of diffusion in polyisobutylene (PIB)-CHCl3 are reconsidered, comparing diffusion coefficients D(p) and D(ch) of silica spheres and random-coil polymers in PIB-CHCl3 solutions. In solutions of low-molecular-mass matrix polymers, D(p)/D(ch) is virtually independent of matrix concentration c; a rapidly-relaxing matrix is equally effective at retarding polymer chains and rigid spheres. On the other hand, in solutions of high-M polymers, with increasing c D(ch) falls far more rapidly than D(p);large-M chains are far more effective at retarding chains than at retarding spheres of the same size. These results are consistent with the hydrodynamic scaling model but are inconsistent with models that grant to polymer chains an additional diffusive mode inaccessible to rigid spheres. D(p) in PIB-CHCl3 follows accurately the universal scaling equation D(p)/D0 = exp(-alpha(cM(gamma))nu).