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Poly(d,l-lactide-co-p-dioxanone)(P(LA-co-PDO)) copolymers with different chain microstructures were synthesized by one-step or two-step bulk ring-opening polymerizations of d,l-lactide(LA) and p-dioxanone(PDO) monomers using stannous octoate [Sn(Oct)_2]/n-dodecanol as the initiating system.The average sequence lengths of the lactidyl(L_(LA)) and dioxanyl(L_(PDO)) units were calculated from the ~1H NMR spectra.It was found that both L_(LA) and L_(PDO) values from the two-step syntheses were significantly longer than those from the corresponding one-step syntheses,indicating more blocky structure achieved for the two-step copolymers.Corresponding to this difference in microstructure,the two-step copolymers were semi-crystalline,while the one-step copolymers were completely amorphous.In conclusion,the crystallinity of P(LA-co-PDO) copolymers could be adjusted conveniently to meet specific applications by changing the microstructure of the copolymers via different polymerization routes.
Poly (d, l-lactide-co-p-dioxanone) (P (LA-co-PDO)) copolymers with different chain microstructures were synthesized by one-step or two-step bulk ring- opening polymerizations of d, l-lactide (LA) and p-dioxanone (PDO) monomers using stannous octoate [Sn (Oct) _2] / n-dodecanol as the initiating system.The average sequence lengths of the lactidyl (LA_) and dioxanyl (PD_) ) units were calculated from the ~ 1H NMR spectra. It was found that both L_ (LA) and L_ (PDO) values from the two-step syntheses were significantly longer than those from the corresponding one-step syntheses, indicating more blocky structure achieved for the two-step copolymers. Duerespond to this difference in microstructure, the two-step copolymers were semi-crystalline, while the one-step copolymers were completely amorphous.In conclusion, the crystallinity of P (LA-co-PDO) be adjusted conveniently to meet specific applications by changing the microstructure of the copolymers via different polymerization routes.