Diffusion of single chains in polymer matrices as measured by pulsed-field-gradient nmr: Crossover from zimm- to rouse-type diffusion

Abstract

To investigate the crossover behavior of chain diffusion from Zimm- to Rouse-type, the tracer diffusion coefficient in poly(dimethylsiloxane) (PDMS) mixtures with no entanglements has been measured by the pulsed-field-gradient NMR (PFG NMR) method. Diffusion coefficient D of single chains (molecular weight M) in polymer matrices (molecular weight M) was reasonably determined as a function of M and M. M and M ranged from 460 to 1.93×10. The crossover behavior has been observed: The Zimm-type diffusion for M, while the Rouse-type for M27M, although the crossover region was rather wide. The results were well described by the simple equation D=D+D, where D and D were the Zimm-type and Rouse-type diffusion coefficients, respectively. © 1992 The Society of Polymer Science, Japan.