Electrochemical preparation and in situ characterization of poly(3-methylpyrrole) and poly(3-methylpyrrole-cyclodextrin) films on gold electrodes

摘要

A Electrosynthesis of conducting poly(3-methylpyrrole) (P3MPy) and poly(3-methylpyrrole-2,6-dimethyl-β-cyclodextrin) (poly(3MPy-β-DMCD)) films on a gold electrode in acetonitrile electrolyte solution containing lithium perchlorate has been carried out by potential cycling. Products were characterized with cyclic voltammetry CV, in situ UV-Vis spectroscopy, and in situ resistance measurements. Electrosynthesis of poly(3MPy-β-DMCD) started with a (1:1) (3MPy-β-DMCD) supramolecular cyclodextrin CD complex of 3-methylpyrrole characterized with proton NMR spectroscopy. The oxidation peak of poly(3MPy-β-DMCD) in CVs is shifted to more positive values than P3MPy. In situ resistance measurements show that the resistance of poly(3MPy-β-DMCD) is higher than of P3MPy by approximately an order of magnitude. Minimum resistance can be observed for P3MPy and poly(3MPy-β-DMCD) at 0.40 < E_(Ag/AgCl) < 1.10 V and 0.60 < E_(Ag/AgCl) < 1.10 V, respectively. The higher resistance of P3MPy compared with polypyrrole may result from the presence of the methyl group substituent resulting in a decreased conjugation length. When CD is present during synthesis, resistance is even higher. In situ UV-Vis spectroelectrochemical data for both films prepared potentiodynamically by cycling the potential in the range - 0.20 < E_(Ag/AgCl) < 1.10 V in acetonitrile electrolyte show major effects of CD presence during electrosynthesis.