Crosslinkable Polyphenols from Urushiol Analogues

Synthesis and curing behaviors of polyphenol from urushiol analogues have been examined. The analogues were synthesized by lipase-catalyzed esterification of 4-hydroxyphenethyl alcohol with unsaturated fatty acids, in which the primary hydroxy group was regioselectively acylated to give the phenol derivatives having the unsaturated group in the para position. The oxidative polymerization of the analogues was performed using iron-salen or peroxidase as catalyst. Under appropriate reaction conditions, an oily soluble polymer was obtained in high yields. NMR analysis of the product polymer showed that only the phenolic moiety was polymerized and the unsaturated group was not involved in reaction during the polymerization. The polymer was subjected to the hardening by cobalt naphthenate catalyst or thermal treatment, yielding crosslinked film (artificial urushi) with high gloss surface.