Research

Alternative Solvents for More Environmental Friendly Polymerization

Ring-opening metathesis polymerization (ROMP) is a type of olefin polymerization that retains the unsaturation of the monomer in the polymer backbone. ROMP has been traditionally achieved with metal alkylidene initiators (Ru, Mo, W), with the residual metal retained in the final polymer.

One method to eliminate metal species in polymers is metal-free ring-opening metathesis polymerization (MF-ROMP). In MF-ROMP, a photoredox catalyst and organic initiator generate a radical cationic species to initiate polymerization when irradiated with blue light. Typically, this reaction is done in dichloromethane (DCM), but there has been increased interest in reducing DCM in industrial chemical processes.

Therefore, we seek to identify alternative solvent systems for MF-ROMP to make it more environmentally friendly polymerization while understanding the properties that make a solvent suitable for MF-ROMP. We demonstrate the effects of different solvent systems on MF-ROMP for a few industrially relevant ROMP monomers.

Presented at 2025 National Graduate Research Polymer Conference at Arizona State University as part of the “Green chemistry approaches to polymer design and synthesis” session

Applications of Metal-Free Ring-Opening Metathesis Polymers

Crosslinking density impacts the material properties of thermosets, but spontaneous crosslinking between alkenes and reactive metal species in metal-mediated ROMP makes it difficult to control the crosslinking density.

Polydicyclopentadiene (PDCPD) is a common thermoset comprised of a crosslinked network of polymer chains. Although the crosslinked network makes PDCPD a high impact resistance material, the inability to control the crosslinking limits the range of material properties.

Therefore, we seek to understand how crosslinking density can be controlled. In this study, the effects of the composition and weight percent loading of linear PDCPD copolymers on the crosslinking density and material properties, such as T_g and mechanical properties, were characterized and evaluated.

Presented at American Chemical Society Fall 2023 San Francisco SciMix Poster Session

Metal Ion Uptake in Lactobacillus Plantarum as a Model Organism for Studying the Human Gut Microbiota

The human body maintains a commensal relationship with millions of microbes, known as the microbiota. Most of these microbes are found in the gastrointestinal tract, where they digest food, take up nutrients, and protect the human body from pathogens. Changes in essential trace metal levels, including Mn2+, Zn2+, and Fe2+, influence the abundance of different types of microbial species and strongly correlate to altered infectious disease susceptibility.

Despite recent efforts to map microbiota chemical functions, the role of metals in this area remains underdeveloped. Towards determining how different gut bacteria can tolerate changes in essential trace elements, we have developed gut bacteria culture methods for growth and quantified the metal ion uptake of Escherichia coli with inductively coupled plasma-mass spectrometry. We compared the growth of E. coli in Luria broth and A minimal media with limited trace metals. Then, we cultured Lactobacillus plantarum in De Man, Rogosa, and Sharpe (MRS) and chemically defined media with limited trace metals.

Lastly, we categorized and identified possible metalloproteins using UniProt to better understand the metalloproteome of L. plantarum. This work will give us insight towards improvement and application of current therapies for gut diseases and potential targets for development of new therapeutics.

Presented at University of Houston 2018 Undergraduate Research Day

Efficient Treatment of Chromium Plating Wastewater Using a Chitosan Composite Polymer

Presented at University of Houston 2017 Undergraduate Research Day