APPLICATION OF DENSITY-FUNCTIONAL THEORY IN THE SYNTHESIS OF ELECTROACTIVE POLYMERS

A wide range of conjugated organic compounds undergo anodic electropol ymerisation to produce polymers of high conductivity. However, electro oxidation does not always result in the formation of electroactive mat erials, since some reactions produce insulating films or soluble oligo mers. Density functional theory (DFT) has been used to predict the out come of electropolymerisation reactions by calculating the unpaired el ectron pi-spin density distribution of monomeric radical cations, in o rder to determine coupling positions in the resultant polymers. pi-Spi n densities calculated for pyrrole, thiophene and (E)-3-stilbene are f ound to be in good agreement with experimental values. DFT has been us ed to investigate the low conductivity and redox inactivity of poly[(E )-3-styrylthiophenes] and poly[(E)-2-styrylheterocycles]. High positiv e spin densities at the alkene spacer linkage in the corresponding mon omeric radical cations were found, suggesting crosslinking of the poly mers via the double bond. In contrast, electroactive polymers of impro ved conductivity are formed from the electropolymerisation of some (Z) -2-alpha,beta-diarylacrylonitriles. For these monomers, DFT calculatio ns show the positions of highest spin density to be located at the ct- positions of the heterocyclic rings, suggesting the presence of alpha, alpha'-linked monomeric couplings necessary for electroactivity.