Date of Completion

8-26-2019

Embargo Period

8-6-2019

Advisors

Professor Rajeswari M. Kasi, Professor Douglas Adamson, Professor Yao Lin

Field of Study

Chemistry

Degree

Master of Science

Open Access

Open Access

Abstract

Anion exchange membrane (AEM) research is primarily focused to develop suitable AEMs with high ion conductivity for high pH and high-temperature environments used in water electrolysis and fuel cells. To address these issue research has been done on improving the ion exchange head group to obtain high ion conductivity and designing a rational polymer architecture to improve chemical and mechanical stability.

Most widely used ionic head groups are based on quaternary ammonium ions due to its high ion conductivity. However quaternary ammonium ion containing membranes degrades with time resulting in low ion exchange capacity (IEC) and low alkaline stability due to its susceptibility to hydroxide ions. Therefore, branching out from quaternary ammonium ion-based membranes research has been widely done on other N containing cations such as imidazolium, pyridinium and guanidium. Out of these imidazolium has shown the most assurance due to its high ion conductivity and adaptable structure for modifications.

In parallel with enhancing the chemistry of the ion exchange moiety research has been done improving the polymer architecture to gain more chemical and mechanical stability. Most widely used polymer backbones are polysulfones and fluorinated polymers, Nafion being the most popular. Nevertheless, literature has highlighted a few major drawbacks of polymer membranes synthesized with these. Polysulfones are susceptible to ether and quaternary carbon hydrolysis and polyfluorines are subjected to dehydrofluorination with time. As a result, research has been done on many other polymer backbones and polynorbornene has attracted much attention due to it’s high thermal and chemical stability, excellent film-forming properties and simple controllable polymerization techniques.

One important strategy to obtain ion conductivity includes having densely functionalized ion-conducting groups on a hydrophobic polymer matrix creating ion channels. Also rather than attaching the ion exchanging head group directly to the polymer backbone having it on regularly spaced flexible side chains improves ion conductivity. Apart from that this architecture is promised to show more alkaline stability due to the polymer backbone being protected by the hydrophobic polymer matrix.

Considering all these facts it is clear that both ion exchange head group and polymer architecture are equally important in designing an AEMs addressing the current issues in the field. In this work we present a series of a novel brush like liquid crystalline imidazolium functionalized norbornene ionic liquid copolymers with ion channels and improved alkaline stability.

Major Advisor

Professor Rajeswari Kasi

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