(449aw) Liquid Methanol Sorption, Diffusion and Permeation in Water Swollen Polymers

Liquid methanol sorption, diffusion and permeation in cross-linked PEGDA (XLPEGDA) and ion exchange polymers based on sulfonated polystyrene has been investigated and compared to sodium chloride transport. Methanol was selected as an uncharged model molecule because of its complete solubility in water.

The mechanism of solutes diffusion in water swollen polymers was experimentally and theoretically analyzed, and the role of the polymer fixed charges was elucidated. In particular, methanol sorption and diffusion in charged and uncharged polymers are ruled by the membrane degree of swelling, with more swollen membranes exhibiting faster transport rates and greater sorption levels. The electrostatic phenomena affecting ion transport in swollen polymers, i.e. ion-ion interactions and Donnan exclusion, are not involved in methanol transport. The extent to which methanol transport rate in the membrane is reduced relative to that in pure water is discussed and related to the membrane water content using the Mackie-Meares model [1]. The issue of convective transport and its effect on the diffusion coefficient were quantitatively addressed.

Finally, Flory-Rehner theory for ternary systems [2] was used to quantitatively interpret methanol sorption isotherms in swollen polymers.

[1] J.S. Mackie et al., Proc. Royal Soc. 1955 232 498-509

[2] P.J. Flory et al., J. Chem. Phys. 1943 11 521-526