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Probing the state of absorbed water by diffusion technique
Author(s) -
Sarbolouki Mohammad N.
Publication year - 1973
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1973.070170807
Subject(s) - porosity , membrane , diffusion , homogeneous , materials science , permeability (electromagnetism) , analytical chemistry (journal) , thermodynamics , chemistry , composite material , physics , chromatography , biochemistry
The diffusion coefficient of water, D wm , across homogeneous cellulose acetate membranes of graded porosity ε (water content) are measured. At high values of porosity, D wm varies monotonously as ε is varied. At a certain porosity ε c , however, there is a sudden change in D wm ; and thereafter the change becomes linear again, but with a different slope. Diffusion coefficients are interpreted, through the Stokes‐Einstein relation, in terms of the overall microscopic viscosities η wm of the membrane matrix. The values of η wm are then correlated with the equivalent pore size r of the membranes. It is discovered that the sudden change in D wm (or η wm ) at ε c correlates with similar changes in other properties such as hydraulic permeability and selectivity of the membrane. All these observations are then attributed to the water structure inside the membranes.