Redox-active polymers by group-transfer polymerization: physical, electrochemical and electronic properties

A variety of redox-active polymers and copolymers containing N,N,N′,N′-tetraalkyl-1,4-phenylenediamine were synthesized, preferentially based on methacrylates and sorbates. Group-transfer polymerization proved to be the polymerization method of choice, in order to protect the rather sensitive functional groups. Electrochemical studies indicated that oxidation of the redox-active group generally occurred at low oxidation potentials (∼0.25 V vs. SCE), generating stable poly(radical ions). Structural variation of the polymers did not alter the redox behaviour significantly. Owing to their low oxidation potential, the polymers are easily oxidized, or form charge-transfer complexes with many electron acceptors. Whereas the native polymers are insulators, exhibiting electrical conductivities smaller than 10^-12Ω^-1cm^-1, exposure to iodine yielded materials that absorbed up to 85% iodine (w/w) with conductivities in the range 10^-2 to 10^-4Ω^-1cm^-1. The conductivities measured are virtually equal for all polymers studied, being rather insensitive to the detailed polymer structure.