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The permeability of water swollen segmented polyurethane membranes has been determined for the solutes urea, glucose, sucrose, and raffinose at 26.5[degrees]C. The permeability of segmented polyurethane membranes; based on poly(oxyethylene glycol) grades 600, 1000, 1500, and 1540; was determined for the swollen unstrained films and for the swollen films at several strains. The free volume theory for diffusion through homogeneously swollen polymers was able to predict the observed changes in membrane permeability with strain for all solutes except urea. The free volume theory fails to predict the urea data accurately because the polyurethanes used absorb urea and therefore the urea can diffuse through the polymer as well as through the solvent, an eventuality not provided for in the free volume theory.

The solute reflection coefficient [...], as defined in the theory of thermodynamics of irreversible processes, was determined. The available-area-ratio and the film tortuosity were calculated from the solute reflection coefficient and the film permeability [...]. Neither the available-area-ratio nor the film tortuosity correlate with changes in the film permeability.

A correlation between [...] and [...] was proposed. It was shown that for [...] the film permeability [...] is inversely proportional to [...]. The proposed correlation is discussed and the suggestion is made that additional experiments be conducted to determine the range in [...] for which the correlation is valid.

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