Session: Modern Methods in Polymer Chemistry:

π-conjugated polymers (CPs) have promise in electronic applications where weight or flexibility are important. The dominant paradigm of step growth polymerization does not allow for sequence or architecture control, limiting the optimization of these materials. Catalyst transfer polycondensation enables a chain growth mechanism, but expanding to new monomer types remains a challenge. Using a mechanistically distinct approach, we utilize photoexcitation to achieve chain growth polymerization by taking advantage of the inherent photophysical properties of CPs. We have discovered that electron deficient Grignard monomers readily polymerize under visible light irradiation at room temperature in the absence of a catalyst. The product distribution can be tuned by the wavelength of irradiation based on the absorption of the polymer. Conversion studies are consistent with an uncontrolled chain growth process; correspondingly, chain extension produces all conjugated n type block copolymers. Preliminary results demonstrate that the polymerization can be expanded to donor acceptor alternating copolymers. Mechanistic studies provide insight into the substrate scope and role of light. We anticipate that this method can serve as a platform to access new architectures of n type CPs without the need for transition metal catalysis.

Prof. Julia Kalow

Assistant Professor, Northwestern University

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