Diffusion of free polydimethylsiloxane chains in polydimethylsiloxane elastomer networks

Abstract

The diffusion of four unreactive polydimethylsiloxane chains of various molecular masses into two polydimethylsiloxane (PDMS) elastomer networks has been studied by a Sorption method. This study shows that the shortest chains penetrate more rapidly than the longest one into a PDMS network. The equilibrium swelling time is also shorter, whereas the degree of swelling (by the unreactive PDMS chains) decreases when the chain length increases. When the mesh size of the network decreases, the diffusion coefficient of the PDMS chain stays unchanged provided that the chain is long enough, but increases in the case of the investigated shortest chain. The selfdiffusion of the PDMS chain (which can be composed of unreticulated chains) in a PDMS network is not negligible and can modify significantly the diffusion of other solutes.