SORPTION AND DIFFUSION OF WATER-VAPOR IN HYDROGEN-BONDED POLYMER BLENDS

Water vapour was used as a diffusional probe to study segmental mobility in hydrogen-bonded polymer blends. Modified polystyrenes containing 4-hydroxystyrene as comonomer units were blended with poly(methyl methacrylate). The diffusion coefficient of water decreased with increasing concentration of the diffusant. Clustering of water molecules in the polymer rendered a fraction of the sorbed water comparatively immobile. A partial immobilization model was used to estimate the diffusion coefficient of the clusters. Interpolymer hydrogen bonding acted as physical crosslinks, which decreased the diffusivity of clusters. However, the positive excess volume of mixing for one blend composition seemed to have nullified the restrictive effect of hydrogen bonding on cluster diffusivity.