Next Generation Catalyst Transfer Polycondensations

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Professor Anne J. McNeil of the University of Michigan Ann Arbor is supported by the Chemical Catalysis (CAT) program in the Division of Chemistry to develop catalytic, synthetic procedures to make polymers that conduct electricity with improved structural control. Conductive polymers represent an interesting subset of polymers that are used as the light-harvesting layer in solar cells, the light-emitting layer in diodes (i.e., LEDs), and the charge conducting layer in transistors. One key advantage of conductive polymers is that they are flexible, and therefore they can be coated onto flexible substrates using simple, high-throughput technologies (e.g., ink-jet printing). Moreover, the starting materials are inexpensive. As a consequence, the conductive polymers market is rapidly growing and expected to reach 1.6 billion dollars in the US by 2017. The goal of this research is to broaden the types of polymers that can be made, and at the same time, increase the user-friendliness of the preparation procedure. Polymers with variable composition along the polymer chain are prepared. The objective is to improve the robustness and lifetime of polymer-based solar cells. The project may have a broader impact on the scientific community and the society at large, given that conjugated polymers are widely used for many applications. During the course of this work, students are trained in organic, inorganic, organometallic and polymer synthesis and characterization, mechanistic organometallic chemistry, solar cell fabrication and testing. Students from historically underrepresented groups are involved in the project through participation in the Michigan Math and Science Scholars Program and the research partnership with Washtenaw Community College. Gradient sequence conjugated copolymers are prepared and evaluated for use as compatibilizers in solar cells. Polymer composition, length, and sequence are all crucial factors that influence the properties of the polymer. As a result, each application often requires different polymer structure to be synthesized. The copolymers are prepared using palladium catalysts following a mechanism known as catalyst-transfer polycondensation (CTP). Current CTP methods, however, have many limitations, including sensitivity to oxygen and moisture and the fact that many functional groups are not tolerated, large monomers are difficult to polymerize, and few electron-deficient monomers have been polymerized. The aim of this research is to identify chain-growth methods that are functional group tolerant and user-friendly, and to enable polymerization of large monomers containing electron-deficient arenes. Once optimized, the methods are applied to the gradient copolymer synthesis of higher-performing polymers (beyond poly (3-hexylthiophene)) with side chain fullerene for compatibilizing solar cells. The resulting mechanistic insight and catalysis discoveries may interest the synthetic organic, organometallic and polymer chemistry communities.