(4b) Sustainable Complex Fluids

In my doctoral work, I studied the polymerization of novel monomers on surfaces for both adhesives and upcycled plastics. The novel monomers, methylidene malonates, undergo anionic polymerization at ambient conditions, in a similar mechanism to cyanoacrylates (e.g. superglue). I examined the polymerization and grafting of these monomers from poly(ethylene-co-acrylic acid) surfaces with both the acid and sodium salt. Using attenuated total reflectance Fourier transfer infrared spectroscopy (ATR-FTIR), we determined that small amounts of carboxylate salt resulted in homogenous grafted polymer. Surprisingly, even the acrylic acid resulted in grafted polymer, despite the low concentration of dissociated anion and literature results indicating that weak acids slow polymerization of cyanoacrylates. Working with my PI and collaborators, I wrote grants and planned experiments to develop biodegradable and chemically recyclable films from biobased monomers that can be processed into low density poly(ethylene) replacements (e.g. plastic bags, packaging film, and other consumer products). As part of the groundwork for this project, we synthesized polyesters with biobased 1,5-pentanediol to replace conventional glycols using vacuum assisted polycondensation in a large (500 mL) reactor. Preliminary synthesis resulted in high molar mass polymers, which we hypothesized would have the mechanical properties necessary for the targeted applications.

After graduation, I started an NRC post-doctoral fellowship at the NIST Center for Neutron Research (NCNR) where I have been studying the structure and rheology of block copolymer micelles and lipid nanoparticles at industrially relevant, high shear rates (≥ 10⁴ s^-1) using simultaneous capillary rheology and small angle neutron and x-ray scattering (rheoSAS). Thus far, we have measured the high shear structure of poly(styrene-co-ethylene glycol) block copolymer micelles over a range of concentrations. For samples with high concentration, the suspensions are soft, gel-like solids: static SANS measurements reveal somewhat broad peaks, suggesting the beginning of crystal-like ordering at these concentrations. While undergoing shear deformation in the capillary rheometer, the samples exhibit a 2D neutron scattering pattern with strong diffraction-like peaks, indicating shear induced crystallization of the micelles. The scattering pattens are particularly remarkable considering the capillary rheometer measures the structure with multiple shear rates due to Poiseuille flow and two shear planes. These results are the first rheoSANS measurements of block copolymer micelles at shear rates > 10⁴ s^-1 to our knowledge.

Research Interests

As a faculty member, I propose to investigate the structure and rheology of complex fluids for applications in sustainable personal care products, pharmaceuticals, and performance polymers for the circular economy. My research goals will incorporate my knowledge of novel monomer polymerization and my strategies for creating sustainable polymers with application-relevant mechanical properties. I will blend these skills from my doctoral work with the expertise I have developed in scattering techniques, rheology, and colloidal particles from my post-doctoral research. My lab will study two main applications challenges: i) designing sustainably derived, performance polymers, including single component polymers with new additives, multicomponent blends, and composites, and ii) re-formulating personal care and pharmaceutical products with sustainably derived ingredients.

Chemical feedstocks based on biological and waste streams contain complex mixtures compared to synthetically derived materials, which have precise control over material properties and purity. Removing the impurities can decrease the financial viability or the relative sustainability of the product (e.g. more energy to perform the separation uses additional resources and is less cost effective).

However, the complexity of these feedstocks can pose challenges to their adoption or change the performance or stability of the final product. To address these challenges, my lab will study the structure and mechanical properties of biological and waste-derived polymers and colloidal formulations.

For many polymers and colloids, the processing and composition affect the nano- and micro-structure, which in turn dictates the mechanical and thermal properties; these material properties can limit or expand the applications for a new polymer, composite, or formulation. My lab will study the fundamental properties of these sustainable materials and develop process-structure-property relationships to aid the design of materials for a circular economy. We will use scattering experiments, including light, x-ray, and neutron scattering, to elucidate the structure of materials on multiple length scales. X-ray and neutron scattering have additional advantages for measuring multicomponent mixtures. For instance, we can use x-ray scattering to differentiate polymers and the higher atomic number materials that are sometimes used as performance additives in composites. Neutron scattering can highlight differences in structure among organic components using deuteration to change the isotopic composition of hydrocarbons. We will use rheology and dynamic mechanical testing to measure the mechanical properties of complex fluids and polymers. By understanding the structure and rheology of the materials, we can tune their response to deformation and formulate materials to meet performance goals for specific applications.

Teaching Interests

As an educator, I am interested in learning new methodologies for teaching core chemical engineering classes, as well as developing courses for a wide variety of students (e.g. classes for non-majors, interdisciplinary classes, and those suited for alternative learning styles). I am committed to critically evaluating my teaching methodology and improving my pedagogy based on ongoing STEM education research to reach students of multiple and diverse backgrounds. I want to help students build a strong foundation in chemical engineering topics at both the undergraduate and graduate level, with specific interests in teaching chemical engineering fundamentals and mass balances, transport phenomena, and thermodynamics.

I am excited to develop new courses featuring experiential learning and focusing on my interests in product design, communication, and the circular economy. I enjoy training others on different instruments and techniques, as well as mentoring others in research planning, writing, and professional development. Given the opportunity, I will use these interests to develop core classes and electives with a holistic approach that strengthens students in technical communication, critical and creative problem solving, safety analysis, and collaboration with interdisciplinary teams.