Oxidative coupling polymerization of 2,6-dihydroxynaphthalene in basic water

Abstract

The oxidative coupling polymerization of 2,6-dihydroxynaphthalene was found to take place in basic water. Alkaline metal bases such as NaOH and K 2CO3 with the catalyst of copper(II) disodium ethylenediaminetetraacetate tetrahydrate resulted in promoting the over-oxidation to form the quinone unit and the C-O coupling to form the ether unit. When amines were employed as the base, their structures affected the polymerization results. HOCH2CH2NH2. and (HOCH2)3CNH2 produced poly(2,6-dihydroxy-1,5- naphthylene) without the quinone and the ether units, however, which were formed in the presence of Me2NH, Me3N, and BnNH2. Surprisingly, it was found that the catalyst was dispensable for amines to promote this polymerization.