A novel synthetic method to obtain highly crystallizable absorbable copolyesters

A series of undyed 90/10 (mol %) poly(p-dioxanone-co-glycolide) block copolymers were synthesized by ring-opening polymerization, with stannous octoate as a catalyst, utilizing various ratios of monofunctional initiator, dodecanol (DD), to difunctional initiator, diethylene glycol (DEG). The effect of using combinations of DD and DEG on supramolecular crystalline morphology and crystallization kinetics of prepared polylactone copolymers is examined using calorimetric, optical, and X-ray measurements. We found, unexpectedly, that the absorbable copolymer made with the specific initiator ratio of 50/50 (mol %) exhibits outstanding crystallization properties, crystallizing at radically faster rate and to a higher extent than its counterparts made with either DD or DEG alone. The nucleation density of this material is extremely high compared to those of the other copolymers in the series and is even higher than that of the homopolymer, poly(p-dioxanone) (PDS). This unusual behavior is partially explained by the large presence of the longest blocky sequences of glycolate moieties which can serve as effective nucleation sites and strongly facilitate subsequent crystallization of the major PDS phase.