Simultaneous doping and crosslinking of polythiophene films

Abstract

We present a click chemistry approach for the synthesis of conjugated redox polymers based on highly regioregular polythiophenes with tunable amounts of pendant redox-active triphenylamine (TPA) groups. After solution-processing doping of homogeneous films was performed electrochemically and chemically by the acceptor F₄TCNQ and the chemical oxidant FeCl₃. We find that doping is accompanied by crosslinking upon electrochemical triggers or by oxidation with FeCl₃ leading to polythiophene films crosslinked via tetraphenylbenzidine (TPB) units. Cyclic voltammetry coupled with in situ absorption spectroscopy and in situ conductance measurements show similar oxidation and conductivity regimes for the backbone and the pendant redox units making the films prone to stable redox switching. Bulk conductivities as high as 8 S cm⁻¹ are measured by four-point-probe, i.e. values comparable to doped regioregular poly(3-hexylthiophene) are reachable. The crosslinking reaction renders the films insoluble in all tested solvents, opening potential applications of the materials in direct contact with organic solvents.