SELF-DIFFUSION AND SPIN SPIN RELAXATION IN CYCLIC AND LINEAR POLYDIMETHYLSILOXANE MELTS

Self-diffusion and spin-spin relaxation measurements have been performed on narrow fraction linear and cyclic polydimethylsiloxane (PDMS) polymers in the melt, by pulsed nuclear magnetic resonance techniques. The effects of ring and chain molecular weight have been studied. The diffusion and relaxation data exhibit interesting molecular weight dependencies, some of which were also found in the bulk visocisty. The relaxation data show a noticeable change in molecular weight dependence at the critical molecular weight for entanglement for both the linear and cyclic polymers. The diffusion data are not, however, sensitive to this critical molecular weight effect.