272438 Characterization of Aluminum-Neutralized Sulfonated Styrenic Pentablock Copolymer Films

Wednesday, October 31, 2012: 10:10 AM
403 (Convention Center )
Geoffrey M. Geise, Deptartment of Chemical Engineering & The Texas Materials Institute, The University of Texas at Austin, Austin, TX, Carl L. Willis, Kraton Performance Polymers, Inc., Houston, TX, Cara M. Doherty, CSIRO Manufacturing Science and Technology, Clayton, Australia, Anita J. Hill, CSIRO Manufacturing Science and Technology, Clayton, VIC, Australia, Timothy J. Bastow, CSIRO Manufacturing Science and Technology, Australia, Jamie Ford, University of Pennsylvania, Materials Science and Engineering, Karen I. Winey, Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, Benny D. Freeman, Department of Chemical Engineering, The University of Texas at Austin, Austin, TX and Donald R. Paul, Chemical Engineering, University of Texas at Austin, Austin, TX

Sulfonated polymers have been widely considered for membrane applications such as desalination, electrodialysis (ED), reverse electrodialysis (RED), and membrane capacitive deionization (CDI).  Further optimization of these materials, however, is needed in order to extend and improve these technologies.  Sulfonate groups are reactive sites that can be used as a platform for chemical modification of the polymer.  In this work, an acid-form sulfonated styrenic pentablock copolymer was suspension-phase neutralized with triethylaluminum in order to prepare an aluminum crosslinked polymer, and a structure/property study was conducted.  Aluminum neutralization was confirmed by 27Al NMR.  The morphology and free volume of the polymers were probed by small angle x-ray scattering (SAXS) and positron annihilation lifetime spectroscopy (PALS), respectively, and the stability of the aluminum-sulfonate group bond against ion exchange to the sodium form was probed by soaking the films in 1 mol/L NaCl for 30 days.  The neutralized polymer sorbed considerably less water than the acid-form precursor due, primarily, to neutralization of the sulfonic acid groups.  As a result, the hydrated neutralized polymer was mechanically stronger than the non-neutralized polymer, but the dry neutralized polymer was more brittle than the non-neutralized polymer.  The material’s permeability to water and salt decreased as a result of the neutralization process in a manner that is consistent with free volume theory.  The material’s water/salt sorption selectivity decreased due to neutralization of the polymer’s fixed charge, but overall, the polymer’s water/salt permeability selectivity increased upon neutralization due to an increase in the material’s diffusivity selectivity, which stems predominantly from the decrease in water sorption and its effect on the polymer’s free volume.

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See more of this Session: Membranes for Water Treatment I
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