Okinawa Institute of Technology
Christine Luscombe grew up in Kobe, Japan. After receiving her Bachelor’s degree in Natural Sciences from the University of Cambridge in 2000, she worked with Profs. Andrew Holmes and Wilhelm Huck in the Melville Laboratory of Polymer Synthesis at the University of Cambridge where her research focused on surface modifications using supercritical carbon dioxide for her PhD. She received the Syngenta Award for best organic chemistry project for her PhD. In January 2004, she joined the group of Prof. Jean Fréchet for her post-doctoral studies where she began her research on semiconducting polymers for organic photovoltaics. She was the recipient of the Lindemann Fellowship and the Trinity College Junior Research Fellowship (University of Cambridge) for her post-doctoral studies.
In September 2006, she joined the Materials Science and Engineering Department at the University of Washington, Seattle. She received a number of young faculty awards including the NSF CAREER Award, DARPA Young Faculty Award, as well as the Sloan Research Fellowship. Her current research focuses on the synthesis of semiconducting polymers for organic electronics and has published >140 papers in this area of research. She is currently serving on the Editorial Advisory Boards for a number of journals including Chemical Reviews, Polymer International, Advanced Electronic Materials, ACS Applied Polymer Materials, Journal of Applied Physics, and Advanced Functional Materials. She is an Associate Editor for Macromolecules, is serving on the IUPAC Polymer Education and Polymer Terminology Subcommittees, and is the President of the IUPAC Polymer Division. She joined the Okinawa Institute of Technology in 2021.
In recent years, direct arylation polymerization (DArP) has attracted increasing interest as a method to prepare conjugated polymers in contrast to conventional cross-coupling polymerizations. The most appealing aspects of DArP are reduced organometallic waste and improved step economy as no organometallic prefunctionalization is required. DArP is distinguished as a sustainable and atom-economic approach for constructing C-C bonds over traditional coupling methods by features including generating benign by-products and only requiring functionalization of one component with routine and bench-stable halogens. However, DArP is not without issue – specifically, selectivity and control over the polymerization can be difficult to achieve.
Synergistic catalysis involves the use of more than catalyst to activate different substrates to enable reactions that were not achievable before. In light of the aforementioned issues related to DArP, our group has been investigating the use of the combination of Pd/Ag or Au/Ag as synergistic catalysts.
Our studies began with the development of a controlled DArP to achieve polymers with targeted molecular weights and low dispersities. Since we were unable to achieve controlled DArP using a single catalyst, we chose to use two metals (i) one that would perform the C-H activation followed by (ii) one that would perform the controlled polymerization. While the achieve molecular weights were quite low, nevertheless, we were able to show some living characteristics for the polymerization.
We then tackled the synthesis of donor-acceptor copolymers using cross dehydrogenative coupling (CDC). While standard DArP involves the cross-coupling between C-Br and C-H groups, CDC entails cross-coupling between C-H and C-H groups. As such, selectivity becomes a very important issue and there must be a way to ensure that only cross-coupling products are obtained and not homocoupling products. In this regard, the Pd/Ag cocatalyzed CDC reaction has been reported to be highly effective, and we were able to uncover the origin of this efficacy. We uncovered that the second chain extension cross-coupling proceeds much more efficiently than the first cross-coupling and the homocoupling side reaction (at least 1 order of magnitude faster) leading to unexpectedly low homocoupling defects and high molecular weight polymers. Based on DFT calculations, the high cross-coupling rate in the second cross-coupling was ascribed to the strong Pd-thiophene interaction in the Pd-mediated C–H bond activation transition state, which decreases the energy barrier of the Pd-mediated C–H bond activation. These results have implications beyond polymerizations and can be used to ease the synthesis of a wide range of molecules where C–H bond activation may be the limiting factor.
Okinawa Institute of Technology