Liquid methanol sorption and transport in water swollen polymers and in ion exchange polymers
Michele Galizia, Donald R. Paul, Benny D. Freeman
J.McKetta Department of Chemical Engineering, 200 E. Dean Keeton Street, 78712 Austin,
and Center for Energy and Environmental Resources, 10100 Burnet Road, 78758 Austin,
The University of Texas at Austin, Texas (USA)
Liquid methanol sorption and transport in cross-linked PEGDA (XLPEGDA) and ion exchange hydrogels has been investigated and compared to sodium chloride transport.
This study is meant as an experimental and theoretical analysis of the mechanisms that rule the sorption and transport of solutes in water swollen membranes. Methanol was used as an uncharged model molecule because of its complete solubility in water. Furthermore, 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. Finally, the diffusion coefficient of liquid methanol in water swollen hydrogels is compared to that in pure water and in glassy thermoplastics, such as PET  and PS . The different diffusion mechanism in these systems is discussed and correlated with their structure.
Flory-Rehner theory for ternary systems  was used to correlate methanol sorption isotherms in swollen polymers with just one fitting parameter. Conversely, the Mackie-Meares model  was used to describe methanol diffusion behavior.
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