Investigation of Multicomponent Transport Phenomena in Nafion 117 and Crosslinked Polyether-based Membranes via In Situ ATR FTIR Spectroscopy

Abstract

This dissertation focuses on understanding transport and co-transport behavior for a series of species in dense, hydrated polymer membranes. The rate of solute transport through a membrane, permeability, is a fundamental property when selecting a membrane for an application of interest. However, it is challenging to characterize multicomponent transport using traditional techniques. This work investigates the transport of multiple components through polymeric membranes via a facile, in situ technique that combines the advantages of in situ characterization with spectroscopy; in situ ATR FTIR spectroscopy. Using this technique, the transport behavior of a series of alcohols and sodium acetate is investigated. The transport behavior of alcohols and their complex mixtures are probed as phenomena such as flux coupling and competitive sorption make prediction of multicomponent transport from single component data challenging, and is poorly understood. First, multicomponent transport in NafionTM 117, a commercially significant cation exchange membrane that has been researched extensively, is investigated for alcohols and complex mixtures of alcohols. Furthermore, a series of PEGDA membranes with varied fractional free volume and PEGDA-PEA-AMPS membranes of varied charge and hydrophobicity were synthesized and characterized for their permeability to methanol, sodium acetate, and their binary mixtures. Large deviations were observed between single component permeability and permselectivity compared to those extracted from multicomponent experiments, with variations of up to a factor of 11, demonstrating the importance of this characterization and technique for investigating membrane transport behavior. Overall, while much remains to be learned in this field, the fundamental understanding gained herein advances our understanding of the role of co-solutes, and membrane characteristics on transport behavior.