Gas sorption and transport in side-chain crystalline and molten poly(octadecyl acrylate)

The gas sorption and transport properties of poly(octadecyl acrylate) are d escribed for the semi-crystalline and molten states. The change in permeabi lity upon traversing the melting point, or permeation switch, was observed to be as high as two orders of magnitude depending on the penetrant. Analys is of gas transport is explained using the Michaels and Bixler model for se mi-crystalline polyethylene. This analysis shows chain immobilization of th e amorphous phase by surrounding crystals to play a significant role in des cribing the penetrant-dependent permeation switch in this side-chain crysta lline polymer. Traditional two-phase models describing crystallites as impe netrable barriers with no effect on amorphous phase properties may explain solubility in this system but do not describe diffusion. The dependence of transport parameters on polymer composition, e.g. side-chain length, is als o discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.