Murray State Theses and Dissertations

Abstract

Ionic liquids (ILs) are useful for many applications due to the tunability of their characteristic properties making these salts ideal for many applications. To further increase possible areas of application for these materials, some ILs can be incorporated into polymer structures to form poly ionic liquids (PILs) or ionenes. The specific ions used within the material will determine the thermal, mechanical, and chemical stability properties exhibited by the polymer. Adjustments can be made to the ion structures during the synthetic process to influence these observed properties.

Fuel cells, batteries, solar cells, and capacitors, all require materials that can withstand high temperatures. With this, phosphonium ionenes are of interest, as these polymers typically display enhanced thermal stabilities when compared to other cations commonly used in ionene structures. The thermal stability of the ionene can be further improved via adjusting the functionality of the phosphonium ion. Perarylation of the phosphonium often leads to the enhanced thermal stability desired for the aforementioned applications. In applications such as the fuel cell, alkaline stability is desired alongside thermal stability. Perarylated phosphonium ions commonly also display the desired chemical stability for this application.

In this project, polyaryletherketone (PAEK)- and Polyethersulfone (PES)- like phosphonium ionenes were synthesized. Initially, bromide monomers were produced via P-C coupling. Anion exchange to [NTf2]- was then completed. These monomers were characterized via DSC, TGA. 1H NMR spectroscopy, 13C NMR spectroscopy, 31P NMR spectroscopy and elemental analysis.

Nickel catalyzed polymerization was then completed to form four different ionenes. Ionene structures varied based upon substituent positioning (m- or p-) and use of either a carbonyl or sulfone linker between the phosphorus atoms. The ionenes were characterized via DSC, TGA, 1H NMR spectroscopy, 13C NMR spectroscopy, 31P NMR spectroscopy, elemental analysis, alkaline stability testing, solubility testing, and DRS.

The desired ionenes were successfully synthesized and the desired thermal and alkaline stabilities were observed. The ion conductivity was lower than desired. Based on the collected data, future research will focus on manipulations of the perarylated phosphonium structure to lower the Tg and increase ionic conductivity, without losing the thermal and alkaline stabilities.

Year manuscript completed

2023

Year degree awarded

2023

Author's Keywords

Chemistry, Poly(ionic liquid), Ionene, polymer

Dissertation Committee Chair

Kevin Miller

Committee Chair

Kevin Miller

Committee Member

Kevin Revell

Committee Member

Sourav Chatterjee

Committee Member

R. Daniel Johnson

Document Type

Dissertation/Thesis

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