Compatibilization of the poly(lactic acid)/poly(propylene carbonate) blends through in situ formation of poly(lactic acid)-b-poly(propylene carbonate) copolymer

The in situ formation of poly(lactic acid)-b-poly(propylene carbonate) (PLA-b-PPC) block copolymers were carried out by the reaction between PLA and PPC in the presence of tetrabutyl titanate via transesterification. Molecular weight measurements and C-13 nuclear magnetic resonance spectroscopy revealed that PLA-b-PPC block copolymers with higher molecular weight were obtained by controlling the reactivity point ratio between PLA chains and PPC chains in PLA/PPC reaction system. The sample with a composition of PLA: PPC540:60 (wt %) and a catalyst amount of 0.5 wt % had a more proportionable reactivity point ratio between PLA chains and PPC chains compared with other samples, resulting in a most conspicuous transesterification and inconspicuous chain scission reaction. Therefore, its high molecular weight fraction (Mw> 40.0 3 10 4) increased 80%. The formation of macromolecular PLA-b-PPC copolymer could strengthen the entanglement between PLA and PPC molecular chains, which resulted in an increased viscosity of blends at low shear rate. In addition, the elongation at break of sample with a composition of PLA: PPC540:60 (wt %) and a catalyst amount of 0.5 wt % was nearly as twice as which without catalyst because of the improving miscibility of PLA domains and PPC matrix by the compatibilization of PLA-b-PPC copolymer. (C) 2017 Wiley Periodicals, Inc.