Takashi Tsujimoto

Enzymatic synthesis and curing of biodegradable crosslinkable polyesters

The lipase-catalyzed synthesisk and curing of polyesters that possess an unsaturated fatty acid moiety in the side chain is described. Lipase-catalyzed polymerization of divinyl sebacate and glycerol in the presence of unsaturated fatty acids produced a crosslinkable polyester possessing the unsaturated group. Candida antarctica lipase showed high catalytic activity for their synthesis. Effects of reaction parameters, such as enzyme amount, temperature, and feed ratio of substrates, have been systematically investigated. The polymerization under reduced pressure improved the polymer yield and molecular weight. Divinyl adipate was also enzymatically polymerized with glycerol and linoleic acid to give the crosslinkable polyester. The polymer obtained using linoleic or linolenic acid, was cured using a cobalt naphthenate catalyst or thermal treatment to give a crosslinked, transparent, polymeric film with a high-gloss surface. The cured film was characterized by pencil-scratch hardness testing and FT-IR spectroscopy. The biodegradability of the obtained film was evaluated by biochemical oxygen demand (BOD) measurement in an activated sludge.

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.