Synthesis of Poly(ester‐anhydrides) Based on Different Polyester Precursors

Abstract

AbstractSummary: Poly(ester‐anhydrides) were synthesised from poly(L‐lactide), poly(D,L‐lactide), and poly(ε‐caprolactone) prepolymers prepared by ring‐opening polymerisation of cyclic esters in the presence of 1,4‐butanediol or ricinoleic acid as co‐initiator. The hydroxyl group end functionality of the prepolymers was converted to carboxylic acid functionality by reaction with succinic anhydride, and the polyester precursors were coupled by melt polycondensation to give poly(ester‐anhydrides). 1,4‐Butanediol was used as co‐initiator to study the properties of poly(ester‐anhydrides) prepared from different monomers, whereas ricinoleic acid was used as co‐initiator to introduce a hydrophobic fatty acid moiety to the polyester precursor. In hydrolysis tests, the poly(ester‐anhydrides) showed a two‐stage degradation comprising a rapid hydrolysis of anhydride linkages within three days, followed by the slower hydrolysis of the remaining polyester oligomer. Weight loss of the poly(ester‐anhydrides) depended most importantly on molecular weight and thermal properties of the polyester precursors; thus, poly(ester‐anhydrides) prepared from low molecular weight prepolymers having thermal transitions below 37 °C showed very fast weight loss.image