ELECTROPOLYMERIZATION RATES OF POLYTHIOPHENE POLYPYRROLE COMPOSITE POLYMER WITH SOME DOPANT IONS/

Pyrrole, thiophene, and a mixture of the two monomers were electrochem ically polymerized to investigate polymerization rates and the morphol ogy change of the polymer matrix, and to improve the aging and cyclic voltammetric behaviors of the polymers. Thiophene was polymerized on a smooth surface of Pt electrode by two steps. The first step was contr olled by electron transfer at the electrical double layer and the othe r by diffusion of the monomer reacting on the immobilized layer consis ting of the precoated thiophene polymer. The electropolymerization rat e of the second step was 1.85 x 10(-4) cm(3) mol(-1) s(-1), which is f aster by 8.63 x 10(2) times than the first step. Some supporting elect rolytes such as KPF6, LiClO4, TBAP, and TBABF(4) were employed in the polymerization reaction to see the effects of dopant anions on the pol ymerization rate, and KPF6 was the fastest one at 2.41 x 10(-6) cm s(- 1). However, owing to its sensitivity to oxygen, LiClO4 was used for t he polymerization that is fairly stable in air and the same rate as KP F6. For the competitive polymerization reaction of the two monomers th e rate of thiophene was found to be about 11 times slower than that of thiophene alone. When the starting concentration of the thiophene mon omer was higher than pyrrole by five times, its portion in the composi te polymer was found to be only 8-10%. However, this level gave desira ble results in terms of redox properties and aging. The resistance aga inst aging was explained by the morphology change, which came from gre at shrinking of its porosity. (C) 1997 John Wiley & Sons, Inc.