Synthesis and curing behaviors of cross-linkable polynaphthols from renewable resources: Preparation of artificial urushi

This paper describes the synthesis and curing of cross-linkable polynaphthols from renewable resources. Naphthol monomers bearing an unsaturated group from renewable triglyceride oils were designed and oxidatively polymerized to produce new cross-linkable precursor polymers. The monomers were prepared by acylation of hydroxynaphthoic acids with unsaturated alcohols, obtained by reduction of natural oils. The oxidative polymerization was carried out by Fe-salen catalyst to give soluble polynaphthols. NMR analysis showed that the naphthol moiety was chemoselectively reacted during the polymerization, yielding the polymers possessing the unsaturated group in the side chain. The resulting polymers were readily cured by thermal treatment or cobalt naphthenate catalyst to give the cross-linked film (artificial urushi) with high hardness and gloss surface.