Electrochemical Copolymerization of Isoindigo-Based Donor-Acceptor Polymers with Intrinsically Enhanced Conductivity and Near-Infrared-II Activity

Donor-acceptor (D-A) polymers have excellent electronic and optical properties that allow for their use in multiple areas of research, ranging from field-effect transistors to biosensing. However, traditional chemical polymerization strategies to form D-A polymers often require extensive purification and generate large amounts of waste. Electro-copolymerization of complex isoindigo-based copolymers is explored as a way to overcome traditional synthetic challenges. Herein, the electropolymerization and characterization of four isoindigo-based D-A copolymers are studied with: II-EDOT-T-3, II-Thio-T-3, II-Thio-T-3-TTDT2, and II-EDOT-T-3-TTDT2. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis are used to confirm the composition of the polymers. Electrochemical impedance measurements show electron-transport resistance (R-e) values as low as 74.7 omega at selected potentials, indicating that highly conductive copolymers are present. These p-doped polymers exhibit absorption bands within the near-infrared region (NIR) with optical band gaps as low as 0.790 eV. Results confirm the electro-synthesized D-A copolymers exhibit excellent optical properties in the solid state and enhanced conductivity relative to conventional polymers; thus, affording materials with uses in a broad spectrum of applications.