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

A series of electronically conducting polymers based on fluorine-substitute d 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-thi enyl)-2,3,5,6-tetrafluorobenzene (pTF4P). Thin films of the polymers were d eposited by electropolymerization from solutions of the monomer and the dop ing properties characterized using electrochemical techniques. The polymers pTHB, pTFP, and pTF2P, exhibited reversible p-doping and n-doping with dop ing densities in the range of 0.15-0.45 electrons per monomer unit for p-do ping and 0.12-0.18 electrons per monomer unit for n-doping. Secondary batte ries were fabricated using these pi-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.