Synthesis and Properties of Poly(d,l-lactide-co-p-dioxanone) Random and Segmented Copolymers

Two different polymerization routes, one-step and two-step bulk ring-opening polymerizations of d, l -lactide (LA) and p-dioxanone (PDO) monermers using stannous octoate [Sn(Oct) 2 ]/n-dodecanol as the initiating system, were employed to synthesize poly(d, l -lactide-co-p-dioxanone) P(LA-co-PDO) random and segmented copolymers with different compositions and chain microstructure. For the two-step copolymers, the average sequence lengths of the lactidyl (L LA ) and dioxanyl (L PDO ) units calculated from the 1 H-NMR spectra were much longer than those values for the one-step copolymers with the same LA/PDO feed ratio. Corresponding to this difference in microstructure, the two-step copolymers were semi-crystalline even when the PDO content was as low as 14.5 mol%, while the one-step copolymers were completely amorphous with PDO content below 60.6 mol%. However, irrespective of polymerization route, both types of copolymers displayed a single glass transition temperature that was in a linear relation with composition. The decrease of maximum decomposition temperature of the copolymers was in accordance with the decrease of L PDO value. The mechanical and degradation properties of the copolymers were significantly affected by both the polymerization route and the chemical composition as well. In conclusion, the properties of P(LA-co-PDO) copolymers could be adjusted conveniently to meet specific applications by changing the composition and microstructure of the copolymers via different polymerization routes.