Amorphous Unsaturated Aliphatic Polyesters Derived from Dicarboxylic Monomers Synthesized by Diels-Alder Chemistry

A versatile method for synthesizing functionalized amorphous degradable polyesters via step growth polycondensation was investigated. A series of dicarboxylic acids and anhydrides were synthesized by Diels−Alder reactions of fumaric acid and maleic anhydride, respectively, with various dienes. The resulting difunctional monomers were reacted with 1,8-octanediol in the presence of tin octanoate catalyst at 160 °C and 30 mmHg for 24 h to form new unsaturated aliphatic polyesters. Each polyester had molecular weight M_n between 1.0 × 10⁴ and 2.0 × 10⁴ g mol^-1 and a polydispersity index near 2.0. All of the materials were amorphous and had glass transition temperatures between −30 and −15 °C. Each polymer repeat unit necessarily featured a double bond, which was exploited to cross-link the materials yielding degradable elastomers. Amine- and ether-containing polyesters were synthesized by using monomers formed from the corresponding polar functionalized dienes. Using this broad cycloaddition scheme, a variety of amorphous, functionalized polyesters were successfully synthesized.