G. Zotti et al., IRREVERSIBLE-PROCESSES IN THE ELECTROCHEMICAL REDUCTION OF POLYTHIOPHENES - CHEMICAL MODIFICATIONS OF THE POLYMER AND CHARGE-TRAPPING PHENOMENA, Synthetic metals, 72(3), 1995, pp. 275-281
Irreversible changes occurring in the electrochemical reduction of som
e polythiophenes in acetonitrile have been investigated by cyclic volt
ammetry (CV), UV-Vis and IR spectroscopy and the electrochemical quart
z crystal microbalance (EQCM). Reduction in the presence of alkali met
al cations (Li+, Na+, K+ and Cs+) does not result in n-doping but in h
ydrogenation of the alkene moieties. The promotion of double-bond satu
ration by alkali metal cations following the order Li+, Na+ > K+ > Cs is attributed to their charge-pinning action which decreases as the i
on radius is increased. Reversible reduction in tetralkylammonium elec
trolyte (n-doping) is accompanied by production of hydroxide ions with
in the polymer which are thereby inserted by subsequent oxidation. The
resulting quinone-like groups are responsible for the CV pre-peaks us
ually observed in conducting polymers after n-doping and previously as
signed to trapped charges.