Associate Professor, Chemistry and Biochemistry
CAREER: SusChEM: Develop Unprecedented Chain-growth Polymerization Method to Access Structurally Defined Hyperbranched Polymers
Polymers, a type of giant molecules with high molecular weights, are found in many facets of everyday life that utilize plastics, rubbers, resins, and foams. To provide robust and affordable polymer materials, one thrust in polymer chemistry is to develop an efficient and inexpensive polymerization method that can prepare well-defined polymers with precisely controlled structures, compositions and dimensions. These polymers could be translated into functional materials for specific applications, such as self-healing materials, nanocomposites, coatings, lubricants, microelectronics and nanomedicines. In this project, funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry, Professor Gao develops a facile one-pot one-batch polymerization method that can prepare functional polymers with highly branched structures and very narrow size distribution. The research program is integrated with an education plan to develop undergraduate-level polymer courses and outreach activities to stimulate academic-industrial collaboration and to engage the participation of local high school students and teachers.
This research seeks to develop a conceptually new polymerization method that applies the copper (Cu)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization of ABm (m is greater than or equal to 2) monomers to form polytriazole-based hyperbranched polymers in one pot. An important feature of this method is the confinement of the Cu catalyst within each hyperbranched polymer molecule, resulting in a chain-growth polymerization mechanism with a linear increase of polymer molecular weight and decreased polydispersity with reaction conversion. In addition, the dangling B group in the linear unit is expected to demonstrate higher reactivity than those in the terminal unit, resulting in a fast conversion of linear unit to dendritic unit in hyperbranched polymers and ultimately achieving a high degree of branching. The research activities provide hands-on laboratory training to the graduate and undergraduate students at Notre Dame in organic synthesis, polymer chemistry, and various characterization techniques. The students are developing presentation skills targeting both expert and non-expert audiences. The broader education and outreach impacts are magnified by: 1) improving the impact of current and new polymer chemistry topics in the undergraduate and graduate curriculum, 2) lecturing at local high schools to raise the public awareness of advanced polymer materials and nanotechnologies, and 3) organizing an annual Notre Dame Polymer Materials Symposium to stimulate academic-industrial collaborations and engaging the participation of high school students and teachers in a local science fair.
Professor Gao’s research focuses on the interdisciplinary field between polymer chemistry and materials science, targeting new methodologies to synthesize functional polymers with controlled nanostructures and subsequently to discover and exploit their novel physical properties. Specific examples of his work to date at Notre Dame include the development of a one-pot polymerization method to produce hyperbranched polymers with uniform structure, the design of an organic porous material with hierarchical pore structures for high performance CO2 adsorption, and the construction of conjugated polymers to study the correlation between photo-excitation and charge separation. These achievements have produced a total of 13 publications, including two papers in the Journal of the American Chemical Society, one paper in the Journal of Materials Chemistry A, two papers in Macromolecular Rapid Communications, and one paper in the Journal of Polymer Science Part A, Polymer Chemistry. In particular, his recent discovery of using confined nanospace to regulate polymerizations and polymer reactions provides a new route to efficiently synthesize nanostructured polymers with sophisticated architectures.
Professor Gao joined Chemistry and Biochemistry in 2011 as an assistant professor after finishing his postdoctoral research at the University of California at Berkeley and Lawrence Berkeley National Laboratory. He received his Ph.D. in 2008 from Krzysztof Matyjaszewski group at Carnegie Mellon University and his M.S. and B.S. in Polymer Chemistry from Fudan University, China. He has co-authored more than 70 peer-reviewed papers and 6 book chapters and is the recipient of the 2010 AkzoNobel Award for Outstanding Graduate Research in Polymer Chemistry from ACS, 2014 Army Young Investigator Program (YIP) award, and 2016 NSF CAREER award.