Date of Graduation

8-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Chemical Engineering

Advisor/Mentor

Keisha B. Walters

Committee Member

Daniel Glatzhofer

Second Committee Member

Karthik Nayani

Third Committee Member

Tammy Lutz-Rechtin

Fourth Committee Member

Wan Shou

Keywords

Ionic Actuators, Magnetism, Poly(ionic liquid)s, Polyelectrolytes, Self-assembly, Stimuli-responsive polymers

Abstract

Poly(ionic liquid)s (PILs) are a fascinating subclass of strong polyelectrolytes formed from polymerizable ionic liquids. As a result of their unique properties and counterion exchangeability, PILs can exhibit conformation structure or material property changes in response to external stimuli such as changes in pH/ionic environment, magnetic fields, and electric potentials. In Chapter 1, a comprehensive review of PILs design as well as their stimuli-responsive behavior is provided. Additional motivation for each dissertation chapter is also discussed. In Chapter 2, magnetically responsive PILs (MPILs) are developed from complexing paramagnetic salts with a random PIL copolymer containing a metal-coordinating co-monomer, acrylamide. A systematic spectroscopic investigation (FTIR, UV-Vis, Raman, XPS) was performed to analyze the influence of the acrylamide comonomer on the paramagnetic transition metal complex and its binding to the polymers. A preliminary investigation into its room temperature magnetic properties through AC susceptometry and magnetic attraction to handheld magnets is also provided. In Chapter 3, self-assembly of these random copolymers is induced through complexation with the surfactant sodium dodecyl sulfate to form magnetically responsive polyelectrolyte-surfactant micellular solutions and films. Micellular self-assembly is examined as a function of surfactant concentration through DLS and ZP measurements for both a cobalt-based MPIL and the corresponding non-magnetic PIL copolymer. Cryogenic transmission electron microscopy and FTIR characterizations provide additional insight into the self-assemble structure. Applied magnetic stimuli responsive is investigated of both the solution structures and drop-cast films, with and without the presence of weak (~0.6 T) magnetic fields, through optical microscopy, AFM, and GISAXS. Chapter 4 completes the investigation of select MPIL copolymers and their polyelectrolyte-surfactant complexes through a thorough vibrating sample magnetometry study as a function of magnetic field strength and temperature. Additional FTIR, DLS, ZP, SEM, and DSC characterizations provide insight into the observed magnetic behavior. In Chapter 5, an all-polyelectrolyte block copolymer comprised of a poly(ionic liquid) block and a weak tertiary amine polyelectrolyte block is synthesized and characterized through a Cu(0) mediated atom transfer radical polymerization. NMR and FTIR spectroscopies confirm the synthesis and provide insight into intermolecular interactions, specifically electrostatics and hydrogen bonding, of the novel block copolymer in dry and solution states. DLS measurements indicate the block copolymer exhibits an expanded network like structure in pure dimethyl sulfoxide solution that collapses on addition to potassium nitrate (KNO3) salt, demonstrating salt responsive behavior. Self-assembly of the block copolymer as a drop-cast film was analyzed with a new technique to PIL systems, namely, a hybrid AFM-IR characterization. The films exhibited different morphology depending on film thickness. Chapter 6 examines the electrical stimuli responsive nature of the block copolymer and its corresponding homopolymer in ionic electro active polymer actuator composites. Ionic liquid was combined with the homo- and block copolymer PILs to decrease glass transition temperature and increase ion conductivity. Key parameters for ionic actuation were investigated, including glass transition temperature (DSC), thermal stability (TGA), ion conductivity (EIS), chemical interactions (FTIR), Young’s modulus (AFM force curves), film morphology (AFM), and actuation behavior to small, applied voltage.

Comments

Appendix E supplemental videos are available online via ProQuest Dissertations.

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