Lawrence J. Hill
Research Projects
Synthesis of stimuli-responsive polymers.
We are interested in the synthesis of organic polymers with tunable degradation rates consisting of three components: degradable linkages, antioxidant pendent groups, and relatively unreactive filler monomers. We have synthesized a polymerization initiator with a boronic ester linkage and we have shown that polymers grown from this initiator are degradable in the presence of hydrogen peroxide (Polymers 2022, 14 (9), 1733). Our next goal is to incorporate antioxidant groups into these degradable polymers, and we are working to synthesize polymerizable ascorbic acid derivatives for this purpose. These antioxidant groups are expected to afford some protection to the degradable linkage, and adjusting the feed ratio of antioxidant monomer to filler monomer will then allow us to tune the rate at which polymer molecular weight decreases in the presence of hydrogen peroxide. These materials with tunable lifetimes and compositions are envisioned as antioxidant additives, degradable packaging, and containers for drug delivery simply by changing the filler monomer to suit the application needs. A scheme explaining the degradation of a boronic ester-functionalized initiator is shown to the left below, and data from the degradation of a polymer with and without a boronic ester linkage are shown to the right below.
Related literature:
Hill, L., Sims, H., Nguyen, N., Collins, C., Palmer, J., Wasson, F. "A Degradable Difunctional Initiator for ATRP That Responds to Hydrogen Peroxide" Polymers 2022, 14 (9), 1733
de Gracia Lux, C.; Joshi-Barr, S.; Nguyen, T.; Mahmoud, E.; Schopf, E.; Fomina, N.; Almutairi, A. "Biocompatible Polymeric Nanoparticles Degrade and Release Cargo in Response to Biologically Relevant Levels of Hydrogen Peroxide." J. Am. Chem. Soc. 2012, 134, 15758-15764.
Synthesis of nanoparticles with modified surface chemistry.
We are interested in using novel synthetic approaches to facilitate the use of nanoparticle technologies in devices. Nanocrystals of tunable size, shape, and functionality have been synthesized for a variety of systems, and electron microscopy images of nanomaterials synthesized by WKU students are shown on the left below. We are investigating synthetic routes using ionic liquids to synthesize technologically relevant materials including cadmium chalcogenide semiconductor particles for solar hydrogen generation and Pt/Co alloyed particles with sharp features for the conversion of CO2 into useful materials. The scheme to the right below summarizes our recently published work on the decoration of noble metals onto semiconductor nanorods.
Related literature:
Ballentine, M. D.; Embry, E. G.; Garcia, M. A.; Hill, L. J. "Deposition of metal particles onto semiconductor nanorods using an ionic liquid." Beilstein J. Nanotechnol. 2019, 10, 718-724.