Our group explores new chemistry related to catalysis and polymer functionalization using the tools and precepts of synthetic organic chemistry to prepare functional oligomers or polymers that in turn are used to either effect catalysis in a greener, more environmentally benign way or to more efficiently functionalize polymers. Often this involves creatively combining the physiochemical properties of a polymer with the reactivity of a low molecular weight compound to form new materials with new functions. These green chemistry projects involve fundamental research both in synthesis and catalysis but has practical aspects because of its relevance to practical problems.
A common theme in our catalysis studies is exploring how soluble polymers can facilitate homogeneous catalysis. Homogeneous catalysts are ubiquitously used to prepare polymers, chemical intermediates, basic chemicals and pharmaceuticals. Such catalysts often use expensive or precious metals or expensive ligands or are used at relatively high catalyst loadings. The products often contain traces of these catalysts or ligands - traces that are undesirable for esthetic reasons or because of the potential toxicity of these impurities. Both the cost of these catalysts of these issues require catalyst/product separation - separations that often are inefficient and lead to chemical waste. These processes also use volatile organic solvents - solvents that have to be recovered and separated. Projects underway in our lab explore how soluble polymers can address each of these problems. Examples of past schemes that achieve this goal in a general way as highlighted in the Figure below.
We also use functional polymers to modify existing polymers. Ongoing projects involve molecular design of additives that can more efficiently modify polymers' physical properties. We also use functional polymers in covalent layer-by-layer assembly to surface polymers' surface chemistry. An example of this work is our use of 'smart' polymers that reversibly change from being water soluble cold to being insoluble and hydrophobic on heating. Such polymers' have been used by us to prepare 'smart' catalysts, 'smart' surfaces and membranes, and to probe fundamental chemistry underlying temperature and salt-dependent protein solvation.
"Using Soluble Polymers to Enforce Catalyst-Phase-Selective Solubility and as Antileaching Agents to Facilitate Homogeneous Catalysis", Yannan Liang, Mary L. Harrell, and D. E. Bergbreiter, Angew. Chem. Int. Ed. 2014, 53, 8084-8087. Two important new concepts described here include the first demonstration of antileaching effects of soluble polymer additives and soluble polymer solvents as well as a demonstration of the potential power of using phase selective solubility of catalysts in minimizing or controlling side reactions.
"Soluble Polymers as Tools in Catalysis", ACS Macro Lett. 2014, 3, 260-265. This invited viewpoint article highlights some future directions in how soluble polymers can facilitate catalysis - a focal point of the Bergbreiter research group.
"Polyolefin soluble polyisobutylene oligomer-bound metallophthalocyanine and azo dye additives", Nilusha Priyadarshani, Chase W. Benzine, Benjamin Cassidy, Jakkrit Suriboot, Peng Liu, Hung-Jue Sung, and D. E. Bergbreiter, J. Polym. Sci., Part A: Polym. Chem., 2014, 52, 545-551. This paper describes how polyisobutylene groups make insoluble species soluble providing a new way to usefully functionalize common polymers like polyethylene or polypropylene.
"Using polymer synthesis, reactions and properties as examples of concepts in beginning organic chemistry", D. E. Bergbreiter, ACS Symposium Ser. 2013, 1151, 35-52. Teaching is an important aspect of my work and this paper (and a J. Chem. Educ. paper referenced therein) provides examples of how I use concepts involved in our basic research in my sophomore course.
"Polyethylene as a Nonvolatile Solid Cosolvent Phase for Catalyst Separation and Recovery", Yanfei Yang, Nilusha Priyadarshani, Tatyana Khamatnurova, Jakkrit Suriboot, and D. E. Bergbreiter, J. Am. Chem. Soc. 2012, 134, 14714-14717. Here we described how a narrow PDI polyethylene wax can be used as a nontoxic and nonvolatile solvent, replacing hazardous toxic organic solvents like hexane in a green and sustainable way.
"Specific Ion Effects on the Water Solubility of Macromolecules", Zhang, Y.; Furyk, S.; Bergbreiter, D. E.; Cremer, P. S. J. Am. Chem. Soc. 2005, 127, 14505-14511. This paper was a collaboration with a colleague's group and explored the analogies between 'smart' polymer solubility we used in surface and membrane chemistry and effects of ions on cold denaturation of proteins.