Electroactive Polymeric Materials for Battery Electrodes: Copolymers of Pyrrole and Pyrrole Derivatives with Oligo(ethyleneoxy) Chains at the 3-Position

Abstract

The electrochemical polymerization of pyrrole derivatized at the 3-position with an oligo-(ethyleneoxy) group was investigated. Two monomers were synthesized, namely, 3-(3,6-dioxaheptyl)-pyrrole (DHPy) and 3-(3,6,9-trioxadecanyl)pyrrole (TDPy), and homopolymerized in a LiClO 4 /propylene carbonate medium. The electrical conductivity of poly[3-(3,6-dioxaheptyl)pyrrole] (PDHPy) and poly[3-(3,6,9-trioxadecanyl)pyrrole] (PTDPy), measured by the four-point probe method, was 0.08 and 15 S cm -1 , respectively. Electrochemical copolymerization of both oligo(ethyleneoxy)-substituted pyrroles with pyrrole led to good quality films which displayed considerably higher electrical conductivity than the homopolymers. The conductivity of the copolymer with DHPy was in the range from 8 to 10 S cm -1 and that with TDPy in the range from 20 to 100 S cm -1 . The cyclic voltammogram of both homopolymers and of the copolymers gave current-potential curves with larger areas (ca. 3 times) than PPy. The copolymer of TDPy and pyrrole showed that it was capable of supplying the same current for a longer period of time than polypyrrole itself. No stability problems were observed with the copolymers in contrast to the homopolymer films, and the samples charged and discharged smoothly. In scanning electron micrography, copolymers showed larger nodules than the homopolymer which entirely cover the surface of the compact layer. The results of the copolymer systems show that they have a high potential as materials for polymeric battery electrodes.