Preparation and Characterization of Insulating Polyphenylene Oxide Films on Platinum Electrodes

Abstract

ABSTRACTPolyphenylene oxide (PPO) polymer films were electrogenerated on Pt substrates from solutions of o-allylphenol (OAP), 2-allyl-4-methylphenol (2A4MP), and 2-allyl-6-methylphenol (2AGMP). Relatively thick (l–20μm) films of the corresponding PPO films were generated from 50 v/o methanol/water solutions of the monomers or at low phenol:KOH concentration ratios. The film thickness depended on the maximum anodic potential to which the electrode was cycled. Films prepared from these solutions were found to be microporous with respect to ion permeability, allowing the oxidation of Br− and reduction of Fe3+ to take place at the Pt surface. Competing oxidation of methoxide ion was found to be the cause of the film porosity and thickening.On the other hand, thin (500–1000Å) coherent insulating films which were impervious to Br− and Fe3+ ions could be deposited from aqueous KOH solutions and from methanolic solutions at high phenol:KOH concentration ratios. The thin films were found to decrease the diffusion rates of hydronium and hydrox hydroxide ions to the electrode surface to a significant degree. As a result, the filmed electrodes could be cycled in neutral saline between +1.5 and −0.2 V vs. SCE with no damage to the film.