Electrochemical manipulation of adhesion strength of polybenzoxazines on metal surfaces: from strong adhesion to dismantling

A novel electrochemical redox process for the manipulation of adhesion of polybenzoxazine thermosets on metal surfaces is reported. The method pertains to the electrochemically driven hydroquinone-quinone redox couple. Several antraquinone based bisbenzoxazines possessing phenyl, benzyl and methyl furfuryl substituents were synthesized and characterized. The antraquinone bisbenzoxazines were shown to readily undergo thermally activated ring-opening polymerization in the absence of a catalyst forming cross-linked networks on metal surfaces. The substituent effect on thermal curing behaviour and thermal stability of the cured polymers were investigated. The strong binding affinities of phenolic hydroxyl groups of the anthraquinone moiety in the cured polymers promote adhesion on the metal surface. Electrochemical oxidation converts hydroquinone groups into quinone moieties resulting in the dismantling of the coated films. The generality of this electrochemical method is demonstrated by initial results on platinum electrodes as well as steel plates.