Water vapour transport in polyethylene oxide polymethyl methacrylate blends

Polyethylene oxide/polymethylmethacrylate (PEO/PMMA) blend films have been obtained by evaporation of CHCl3 solutions. The miscibility of the components has been studied by optical microscopy and by differential scanning calorimetry (DSC). The 10/90 blend is miscible while the other compositions are biphasic in the amorphous part of the film, the components being either immiscible or partly miscible. The permeability to water vapour could be interpreted using the conventional series and parallel models for non miscible blends and the logarithmic mixing rule for miscible blends on the condition that only the amorphous phase is considered to be effective in the transport properties. In the 90/10 and 80/20 blends and in the pure components, the sorption isotherms are of the Flory-Huggins type. Sorption kinetics indicates that the permeant mobility and polymer segment relaxation rate are of the same order of magnitude (0.5 < n < 1). Zimm and Lundberg clustering functions were tentatively evaluated and the engaged species induced clustering (ENSIC) model applied to PEG, PMMA, their 80/20 blend and other polymers for comparative purposes. (C) 1999 Elsevier Science Ltd. All rights reserved.