Microwave-assisted synthesis and characterization of biodegradable block copolyesters based on poly(3-hydroxyalkanoate)s and poly(D,L-lactide)

Microwave (MW)‐assisted ring‐opening polymerization (ROP) provides a rapid and straightforward method for engineering a wide array of well‐defined poly(3‐hydroxyalkanoate)‐b‐poly(D,L‐lactide) (PHA‐b‐PLA) diblock copolymers. On MW irradiation, the bulk ROP of D,L‐lactide (LA) could be efficiently triggered by a series of monohydroxylated PHA‐based macroinitiators previously produced via acid‐catalyzed methanolysis of corresponding native PHAs, thus affording diblock copolyesters with tunable compositions. The dependence of LA polymerization on temperature, macroinitiator structure, irradiation time, and [LA]0/[PHA]0 molar ratio was carefully investigated. It turned out that initiator efficiency values close to 1 associated with conversions ranging from 50 to 85% were obtained only after 5 min at 115 °C. A kinetic investigation of the MW‐assisted ROP of LA gave evidence of its “living”/controlled character under the experimental conditions selected. Structural analyses and thermal properties of biodegradable diblock copolyesters were also performed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 poly(3‐hydroxyalkanoate)‐block‐poly(D,L‐lactide) (PHA‐b‐PLA) diblock copolymers with tunable compositions and controlled block lengths were synthesized within short reaction times (typically a few minutes) upon microwave irradiation through the ring‐opening polymerization of D,L‐lactide (LA) triggered by a series of monohydroxylated PHA‐based macroinitiators. A kinetic investigation gave evidence of the “livingness” associated with the mechanism of microwave‐assisted LA polymerization under the experimental conditions selected.