Effective Control of Poly(L-lactide-co-ε-caprolactone) Chain Microstructure Through Polymerization with Different Catalysts and Delayed Co-Monomer Addition

Poly(L-lactide-co-ε-caprolactones) (PLCL) are promising biodegradable polymers with tunable properties for various biomedical applications. Along with the composition, the microstructure of PLCL chain is an important factor affecting its properties, crystallinity, and degradation profile. In this study, to find effective ways for tailoring the microstructure of PLCL chain, kinetic patterns of L-lactide/ε-caprolactone (75:25) ring-opening copolymerization in the presence of two different catalysts were evaluated. The kinetic studies, accompanied by the assessment of the evolution of PLCL microstructure over the reaction course, provided the optimal regimes for synthesis of PLCL with a fixed composition (LA:CL = 75:25) and different chain microstructure. This was achieved by employing two types of catalysts (tin(II) 2-ethylhexanoate and zirconium(IV) acetylacetonate) and delayed co-monomer addition approach. The control of average LA block length (lLA) was achieved in a wide range from 4 to 14 monomeric units. Differential scanning calorimetry and wide-angle X-ray scattering revealed a pronounced effect of lLA on glass transition temperature, melting temperature, and crystallinity.