In vitro degradation behavior of l-lactide/trimethylene carbonate/glycolide terpolymers and a composite with poly(l-lactide-co-glycolide) fibers

Abstract A series of high molar mass terpolymers are synthesized by ring-opening polymerization of l -lactide (LLA), 1,3-trimethylene carbonate (TMC) and glycolide (GA). In vitro degradation of the obtained terpolymers was realized in phosphate buffered saline (PBS) at 37 °C for one year, in comparison with PLLA-TMC copolymer and a composite made up of a PLLA-TMC-GA terpolymer matrix reinforced by poly( l -lactide- co -glycolide) (PLGA) fibers. Degradation was characterized as a function of incubation time by using GPC, DSC and 1 H NMR. PLLA-TMC-GA terpolymers degrade faster than PLLA and PLLA-TMC because of lower chain regularity and lower crystallinity. In the case of the composite, the fast degradation of PLGA fibers speeds up the degradation of the PLLA-TMC-GA matrix due to internal autocatalysis. Morphological changes with increase of melting enthalpy were observed in all cases with crystallization of degradation by-products and selective degradation of amorphous domains. On the other hand, compositional changes appeared more complex since different phenomena are involved, including crystallization of LLA component, selective degradation in amorphous domains, and release of soluble oligomers. Among the various polymers, PLTG90/10/5 and PLTG95/5/5 present appropriate degradation rates, and are promising for the fabrication of totally bioresorbable stents.