No description available.

Sulfonated poly(arylene ether sulfone)s are a class of engineering thermoplastics well-known for their mechanical properties and chemical/oxidative stability. The research in this dissertation focuses on modifying the structure of sulfonated poly(arylene ether sulfone)s to improve membrane performance. Blends of a 20% disulfonated poly(arylene ether sulfone) (BPS20) with poly(ethylene glycol) (PEG) were investigated with the objective of promoting water flux across a reverse osmosis membrane. It was considered desirable to investigate poly(arylene ether sulfone)s with a hydroquinone unit that could be controllably post-sulfonated without degradation, providing a polymer with controlled sulfonation through controlling hydroquinone content. It also avoided the disadvantages noted previously in polymers with post-sulfonated biphenol units. Initial experiments focused on determining sulfonation conditions to confirm quantitative sulfonation of the hydroquinone without side reactions or degradation. A polymer with 29 mole % hydroquinone-containing units was used to study the rate of sulfonation. Successful post-sulfonation was confirmed and reaction conditions were applied to a series of polymers with varying hydroquinone comonomer contents. These polymers were sulfonated, characterized and evaluated for transport properties. Of interest was the high sodium rejection in the presence of calcium, which in the directly copolymerized disulfonated materials is compromised. The post-sulfonated poly(arylene ether sulfone)s showed no compromise in sodium rejection in a mixed-feed of sodium chloride and calcium chloride. In the membrane electrolysis of water, Nafion's high permeability to hydrogen, particularly above about 80 C, results in back-diffusion of hydrogen across the membrane. This reduces efficiency, product purity, and long-term electrode stability. Hydrophilic-hydrophobic multiblock copolymers based on disulfonated and non-sulfonated poly(arylene ether sulfone) oligomers feature a lower gas permeability. Various multiblock compositions and casting conditions were investigated and transport properties were characterized. A multiblock poly(arylene ether sulfone) showed a significant improvement in performance over Nafion at 95°C. Multiblock hydrophilic-hydrophobic poly(arylene ether sulfone)s have been extensively investigated as alternatives for proton exchange membrane fuel cells. One concern with these materials is the complicated multi-step synthesis and processing of oligomers, followed by coupling to produce a multiblock copolymer. An streamlined synthetic process was successful for synthesizing membranes with comparable morphologies and performance to a multiblock synthesized via the traditional method. / Ph. D.

No description available.

It had been shown that the transport properties of CMS membranes varies as a function of H₂S exposure making the conditioning protocol an important step in identifying the steady state properties of CMS membranes. In this study the conditioning of CMS membranes with H₂S was studied for the determination of the acid gas steady state transport properties. The conditioned steady state has been shown to be the same state for both an extended conditioning protocol using high pressure mixed gas and a rapid conditioning protocol using pure H₂S. The rate of conditioning does vary between the two conditioning protocols as the rapid conditioning protocol takes 48 hours less to reach the conditioned steady state. The results of this study also show that oxygen doping during the formation of the CMS membrane affects the final, conditioned steady state transport properties.