STUDIES OF SELF-DIFFUSION OF POLY(DIMETHYLSILOXANE) CHAINS IN PDMS MODEL NETWORKS BY PULSED FIELD GRADIENT NMR

The authors have measured the diffusion of poly(dimethylsiloxane) (PDMS) chains in PDMS model networks by using a pulsed field gradient NMR technique. The model networks have been prepared by tetrafunctional endliking of linear PDMS chains having molecular weights Mn of 3,700 and 7,400 g mol-1. The diffusants have been incorporated in the networks by immersing pieces them in PDMS linear chains with molecular weights Mn between 3,000 and 12,000 g mol-1 and molecular weight distributions Mw/ Mn between 1.1 and 1.7. Although spin-echo attenuation results were fitted to a model which takes into account polydispersity of the diffusant, these results did not exhibit any dependency upon the molecular weight distribution.