(506g) Side Chain Engineering of Conjugated Grafted Polymers for Electrochemical Transistors

Electrochemical transistors are promising devices that may lead to new applications in bioelectronics. The mechanical mismatch between bioelectronic devices and biological tissue can lead to problems with long-term stability, thereby motivating the need for soft conducting materials. To this end, this work describes the synthesis of conjugated grafted polymers as organic electroactive materials. The targeted brush architectures are hypothesized to provide soft mechanical properties due to reduced polymer entanglements.

We describe the synthesis of three schemes of conjugated grafted polymers those with non-conjugated poly(ethylene oxide), conjugated acceptor poly(3-hexylthiophene), or conjugated donor poly(2-(2-heptadecyl)-benzotriazole) side chains. Using coupling techniques (Suzuki Coupling and Kumada Coupling) and controlled radical polymerizations (reversible addition-fragmentation chain-transfer and atom transfer radical polymerization), we have synthesized poly(carbazole) and poly(carbazole-co-benzene) polymer backbones functionalized with azide groups on each repeat unit. Using these techniques, we also synthesized poly(ethylene oxide), poly(3-hexylthiophene), and poly(2-(2-heptadecyl)-benzotriazole) end capped with alkyne groups as our side chains. We utilized a grafting-to approach with a copper-catalyzed azide-alkyne cycloaddition to tether the side chains to the backbones. High-temp NMR was used to verify chemical composition and determine molecular weight. UV-vis absorbance spectra and fluorescence spectra of these grafted polymers were compared to blends containing the same polymer composition by weight. Mechanical properties were characterized using rheology and conductive properties using organic thin-film transistors and electrochemical transistors.