A novel biodegradable polyester with hydrophilic pendant group - Synthesisand ring-opening polymerization of 3-benzyloxymethyl-1,4-dioxane-2,5-dione

The synthesis of a new cyclic ester, 3 - benzyloxymethyl - 1, 4 - dioxane - 2, 5 - dione (3 BMG), was described, which is a precursor of a novel poly (a - hydroxy acid). As an important intermediate, 3 - benzyloxy - glyceric acid (3 - O - BGA) was obtained and first isolated as white needle crystal using 3 chloro - propandiol as starting material. Polymerization of 3 - BMG was carried out in bulk at 140 degreesC with stannous 2 - ethyl hexanoate [Sn(Oct)(2)] as catalyst. High molecular weight of polymer obtained indicat es that the polymerization behavior of 3 - BMG is similar to that of common lactides or lactones. 3 - BMG can also be polymerized by the bimetallic (A l/Zn) alkoxide initiator. The resulting polymer undergoes hydrogenolysis at atmospheric pressure in the presence of a palladium on charcoal and the pe ndant benzyl group was removed completely. The glass transition temperature ( Tg) of the polymer decreases after deprotection. And the deprotective po lymer has melting temperature around 120 degreesC. The data of water absorb ing and contact angle determinations suggest that the hydrophility of the p olymer was improved obviously after deprotection.