Comparative study of isomeric polyalkylterthiophenes with regular regiochemistry of substitution: Characterization of electrochemical doping process

In this paper we present a systematic study of the effect of the substituti on pattern in the starting monomers on the resulting properties of some ele ctrodeposited polydidodecylterthiophenes. The compared characterization of p-doping processes in regioregular electropolymerized poly-3',4'- and 3,3 " -didodecyl-2,2':5',2 "-terthiophene is here reported for the first time. Th e in situ variations of the optical, magnetic, and electrical transport pro perties have been measured and correlated with the effects associated to th e substituent position. An important result was the verification of absorpt ion fine structures in the wavelength range 500 < lambda < 620 nm for the o ptical spectra of the electropolymerized polydidodecylterthiophenes thus co nfirming the typical features of regioregular polymers. Visible spectra and cyclic voltammetries verified that poly-3,3 "-didodecyl-2,2':5',2 "-terthi ophene possessed a more effective electronic conjugation with respect of th e other isomer poly-3',4'-didodecyl-2,2': 5',2 "-terthiophene. On the other hand the latter polymer showed a higher value of the electronic conductivi ty (33 vs 21 S cm(-1)). Such differences were discussed in terms of the eff ect of the substituent position on the polymers packing and the separation between chains.