MODELING THE GROWTH AND MOLECULAR-STRUCTURE OF CONDUCTIVE POLYMERS - APPLICATION TO POLY(DIALKOXYBENZENE)S

A modeling strategy, based on (i) quantum semiempirical calculation of the electronic structure of the successive intermediate oligomers and (ii) evaluation of the activation energy of the successive coupling r eactions by use of the frontier orbital model, has been used to study the growth of a wide set of conductive polymers and is illustrated wit h poly(1,2-dialkoxybenzene) and poly(1,4-dialkoxybenzene) generated by electrochemical oxidation of the corresponding monomer. These monomer s have been chosen because they are known to yield polymers of complet ely different structures. The strategy, which is designed to be as lit tle computer time-consuming as possible, allows us to predict a growth trend in agreement with the structure inferred from spectrochemical e xperiments. In the case of poly(1,2-dialkoxybenzene) it suggests the f ormation of a cyclic tetramer as a byproduct detected in small quantit ies by means of MALDI spectroscopy. This modeling strategy allows one to describe the electronic modifications induced by the growth of a hi ghly conjugated structure. It suggests that oxidation of the successiv e oligomers at high doping level and quinonic deformation are key fact ors for the growth of long and regular polymer structures.