(4as) Exploring the Impact of Metal Coordination and Nanostructure on Magnetically Responsive Poly(ionic liquid) Copolymers and Surfactant-Complexes.

Magnetic poly(ionic liquid)s, or MPILs, are a subclass of magnetically responsive strong polyelectrolytes that are developed through the incorporation of paramagnetic counterions (e.g., [FeCl₄^-], [CoCl₄]^2-). In most MPIL studies, the metal salts are believed to form tetrahedral paramagnetic counterions which bind to the polymer through electrostatic interactions. As the MPIL field continues to grow, more investigation into multicomponent systems is needed to inform the design of these materials to both enhance their magnetic properties expand their application into applied magnetic stimuli-responsive fields, such as directed self-assembly. Co-materials and chemistry that contain metal coordinating functional groups (e.g., amides, sulfonates) can impact both the paramagnetic properties of the transition metal complex and their binding of the metals to the polymer. In this project, the PIL co-polymer, poly(acrylamide-co-diallyl dimethyl ammonium chloride), was systematically complexed with Fe³⁺ or Co²⁺ chloride salts to form a series of MPIL copolymers. A suite of spectroscopic characterizations, including FTIR, XPS, UV-vis, and Raman, were performed to analyze the transition metal complex formation and its binding to the polymer. Select MPIL copolymers were also complexed with sodium dodecyl sulfate to form self-assembled nanostructures structures from polyelectrolyte-surfactant complexes. The magnetic properties of the MPIL copolymers and MPIL-surfactant complexes were examined with A.C. susceptibility and vibrating sample magnetometry (VSM) as a function of metal content and temperature. Dry powders from both MPIL copolymers and surfactant complexes were magnetically responsive to a handheld magnet. The MPIL copolymer-surfactant complexes further demonstrated magnetically influenced structural alignment when dried in a magnetic field as shown with GI-SAXS measurements.

Research Interests :

In addition to magnetically responsive materials, my PhD research work has also involved exploring the use of poly(ionic liquid)s in self-assembly of soft nanomaterials and as electrically responsive actuators. I am interested in pursuing several research areas including electrically responsive textiles and sensors, polymer synthesis and characterization, polymer self-assembly and stimuli-response, and polymer-nanoparticle or gel composites.

My research has led to 4 first author journal articles in print as well as 3 manuscripts under review or in preparation and 12 (inter)national conference talks and presentations. In addition to participating in collaboration with both industry and national laboratory research projects and characterization work, I have extensively contributed to the development of 10 grant proposals to ACS, DoD, USDA, AWRC, and national lab user proposals during my postdoctoral work. During my academic career, I was involved in multiple leadership roles in several student-lead organizations, including the Chemical Engineering Graduate Society and the Society of Plastic Engineers as well as mentoring of both graduate (3) and undergraduate (14) students.

Self-assembly and ion-responsive block copolymers: PILs combined with a co-polymers or surfactants can self-assemble into microphase separated regions in the bulk which can enhance specific material properties such as ion conductivity, mechanical properties, or chemical bonding. This self-assembly behavior is particularly important for developing materials with favorable properties for electrochemical applications such as solid battery electrolytes and flexible electronics. In solution, PILs can form unique nanostructures which lead to interesting fluidic properties. I have focused on synthesizing and exploring the self-assembly behavior of PILs combined with weak polyelectrolytes and examining their nanostructure and chemical bonding interactions in response to added salts in both the bulk and solution states.

Electrically Responsive Ionogels: The inherent ion conductivity and compatibility of PILs with ionic liquids make them excellent candidates as solid electrolytes in ionic electromechanical actuators and sensors. PILs have been able to achieve microscale actuator behavior, but a balance between both high ion conductivity (ideally ≥ 10^-4 S/cm) and moderate mechanical properties (e.g., modulus ~100 MPa) is needed to improve the response time and bending behavior of PIL-based actuators. My projects in this area focused on synthesizing an all-polyelectrolyte block copolymer and evaluating reinforcing agents to improve the actuation behavior of PIL-based actuators. In addition to the actuation behavior, I studied in-depth essential material properties of the ionogels, including ion conductivity, glass transition temperature, thermal stability, mechanical modulus, and chemical interactions.

Fibers: My master’s work involved investigating the successful use of air foils on the optimization of the melt blowing process, a polymer processing technique for forming nonwoven polymer fiber mats. During this work, I utilized high speed and IR thermal photography to evaluate the impact of air foils on fiber attenuation in the high velocity airfields used in the melt blowing technique. I am currently interested in learning and exploring other fiber spinning techniques, such as electrospinning, that can be combined with my experience in strong polyelectrolytes to develop smart textiles and flexible electronics.

Key Words: poly(ionic liquid)s, ionic liquids, ionogels, stimuli-responsive polymers, magnetic and electrically responsive polymers, controlled ‘living’ radical polymerization, block copolymers, polymer processing, fibers.

Teaching Interests: During my graduate career, I quickly discovered a passion for sharing my fundamental knowledge and understanding of chemical engineering with the next cohort of STEM students. I was fortunate to participate in several teaching assistantships in core chemical engineering courses—including Reaction Engineering and Kinetics, Mass and Heat Transport, Separations, and Process Design and Safety—and serve as an AT&T Summer Bridge Chemistry course developer and instructor for in-coming freshman. With my background in polymers and materials research, I am also eager to develop a Polymer Science and Processing course or a Materials Characterization course at the senior undergraduate or graduate level and mentor new graduate students in polymer synthesis and characterization research. I strongly believe that for science and innovation to thrive, it needs the perspectives and contributions from groups of all kinds of diversity. I eagerly await the opportunity and privilege to serve as a professor and continue teaching the next generation of chemical engineers as well as serve as a role model for women engineering.

Select First Author Articles

1. Kayla Foley, Keisha B. Walters. “Solution and Film Self-Assembly of a Block Copolymer Composed of a Poly(ionic liquid) and a Stimuli-Responsive Weak Polyelectrolyte,” ACS Omega, 8(37):33684–33700. DOI: https://doi.org/10.1021/acsomega.3c03989
2. Kayla Foley, Lucas Condes, Keisha B. Walters. “Influence of metal-coordinating comonomers on the coordination structure and binding in magnetic poly(ionic liquid)s,” Syst. Des. Eng., 2023,8, 1402-1417 DOI: https://doi.org/10.1039/D3ME00076A
3. Kayla Foley, Keisha B. Walters. (2022) “Development of Nano- and Micro- Fluids Using Magnetic Poly(ionic liquid)-Surfactant Complexes for Stimuli Response,” Proceedings of the ASME 2022 Fluids Engineering Division Summer Meeting. Volume 2: Multiphase Flow (MFTC); Computational Fluid Dynamics (CFDTC); Micro and Nano Fluid Dynamics (MNFDTC), V002T06A006. DOI:1115/FEDSM2022-87758.
4. Foley, K. A., Shambaugh, R. L. (2018). “Fiber spinning with airfields enhanced by airfoil louvers,” Textile Research Journal, 89(15):3150-3158, DOI: 1177/0040517518807444