The acid-catalysed polycondensation of 2-acetoxymethylthiophenes. Kinetics and mechanisms

This article describes the kinetics and mechanism of the acid-catalysed polycondensation of 2-acetoxymethylthiophene and its C3 and C5 methylated homologues. Numerous experiments were carried out by varying different parameters, such as temperature, solvent and acidic catalyst concentration. The presence of a methyl substituent at C3 or C5 position did not affect the qualitative features of the polymerisations, whereas their rates were enhanced owing to the donor character of the appended substituent. All reactions followed a first order behaviour with respect to the monomer and the activation energies were all around 50 kJ mol−1. The DP of these products grew as a function of reaction time to reach values of about 40 at complete monomer consumption and thereafter chain growth could be reactivated by further monomer additions. Initiation in the presence of added polymer led to its grafting with a substantial increase in molecular weight. The evidence gathered suggests these polycondensations bear a living character.