REDOX SWITCHING MECHANISM OF POLYTHIOPHENES

Spectroelectrochemical studies of the anodic and cathodic redox proces ses of polymers of 3'-substituted 2,2':5',2''-terthiophenes provide in formation on the redox switching mechanism of polythiophenes. A simple chemical model is to describe the neutral polymer as the mixture of t wo species n1 and n2, the effective conjugation length of n2 being twi ce that of n1. In the redox processes n1 and n2 are oxidized (or reduc ed) to mono and diions, respectively. Interconversion of n1 and n2 occ urs through a dimerization/dissociation reaction. Direct evidence on t he symmetry of the cathodic and anodic processes is obtained in the vo ltammetric and spectroscopic behaviour of poly[3'-(2-thienyl)-terthiop hene]. The redox switching mechanism of conducting polymers is not yet clarified in every respect, the problem of interpretation of the tran sformation between the insulating and conducting forms of the polymeri c film is not yet unambigously solved[1-16]. It is thought that spectr oelectrochemical studies on the anodic and cathodic switching of diffe rent poly(3'-substituted 2,2':5',2''-terthiophenes) (Fig.1.) could giv e further information about the processes occurring during the transfo rmation between their insulating and conductive forms owing to a hopef ully more regular structure compared to polythiophene considering the molecular level effect of the substituent on the properties of the pol ymer[2,12].