Synthesis of Polymandelide: A Degradable Polylactide Derivative with Polystyrene-like Properties

Abstract

Polymandelide, an aryl analogue of polylactide, was synthesized by the ring-opening polymerization of mandelide, the cyclic dimer of mandelic acid. The poor solubility of rac-mandelide limited the synthesis of polymandelide via solution polymerization, but polymerization of mandelide at 70 °C as a heterogeneous slurry in acetonitrile yielded first-order kinetic plots and polydispersities <1.2. High molecular weight polymer prepared by melt polymerizations at T > 150 °C exhibit properties that mimic those of polystyrene. Polymandelide is a glassy amorphous polymer with a Tg of 100 °C, with rheological properties comparable to polystyrene, and thermal gravimetric analyses under nitrogen show that the polymer is stable to ∼300 °C. Racemization during polymerization precluded formation of a crystalline polymer. Degradation of polymandelide in pH 7.4 buffer at 55 °C is consistent with a bulk erosion model and, due to its high Tg, proceeds at ∼1/100 the rate of polylactide under similar conditions.