Electrochemical synthesis and characterization of a series of fluoro-substituted phenylene-2-thienyl polymers

A series of electronically conducting polymers based on fluorine-substituted phenylene thienyl have been synthesized. The series includes poly-1,4-bis(2-thienyl)benzene (pTHB), poly-1,4-bis(2-thienyl)-2-fluorobenzene (pTFP), poly-1,4-bis(2-thienyl)-2,5-difluorobenzene (pTF2P), and poly-1,4-bis(2-thienyl)-2,3,5,6-tetrafluorobenzene (pTF4P). Thin films of the polymers were deposited by electropolymerization from solutions of the monomer and the doping properties characterized using electrochemical techniques. The polymers pTHB, pTFP, and pTF2P, exhibited reversible p-doping and n-doping with doping densities in the range of 0.15-0.45 electrons per monomer unit for p-doping and 0.12-0.18 electrons per monomer unit for n-doping. Secondary batteries were fabricated using these π-conjugated polymers as cathode and poly-3-(3,4,5-trifluorophenyl)thiophene (pTFPT) as the anode. On discharge, the cells exhibited an average potential of 2.75 V and charge capacities of 15-20 mA h g^-1, based on the polymer mass and a 100% depth of discharge.