Electrosynthesis of polyamino-benzoquinone (PAQ) polymers

The formation of polyamino-benzoquinone (PAQ) polymers is important in the context of their ability to bind to metals with sufficient affinity to displace water [1,2]. Such polymer formation occurs spontaneously between amine /d iamines and benzoquinone; firstly, it yields a monosubstituted hydroquinone (H2Q) through 1,4-addition. This has to be reoxidised to monosubstituted benzoquinone (BQ) before it can react with the second amine, again through 1,4-addition. Excess BQ is needed to oxidise the disubstituted hydroquinones that are formed as the chain propagation occurs, the rest being converted to H2Q as waste [3]. Further, the H2Q competes with PAQ in binding to the metal and hence needs to be eliminated. The strategy for enhancing the utilisation of BQ molecules warrants the use of oxidising agents such as calcium hypochlorite which in turn needs a phase transfer catalyst, since PAQ formation is usually carried out in non-aqueous media [4]. For complete utilisation and conservation of BQ, it is worthwhile to consider the oxidation of H2Q itself as a precursor to PAQ synthesis using efficient oxidative methods. To meet this end, we provide here a simple electrochemical approach to prepare PAQ polymers either by (i) incorporating BQ units through the oxidation of H2Q into the preformed conducting polyamine films (using its electroinactive potential region) or (ii) through co-deposition of electro-oxidised diamine leading to growing polyamine chains and H2Q units simultaneously in