Preparation and characterization of PLLA/P(CL-b-LLA) blends by an in situ ring-opening polymerization

This paper describes a new reactive blending approach to improve the compatibility of poly(l-lactide) (PLLA) and poly(ɛ-caprolacton) (PCL). For this purpose, the ring-opening polymerization of l-lactide (LLA) was carried out in the presence of PCL-OH (OH groups on one end). The P(CL-b-LLA) block copolymers were in situ formed during polymerization, and as a result, PLLA/P(CL-b-LLA) blends were obtained. The characterization of GPC and 1H NMR verified the synthesis of PLLA/P(CL-b-LLA) blends. Furthermore, the 13C NMR spectroscopy showed that no transesterification reaction occurred to a significant extent during LLA polymerization process. The in situ formed P(CL-b-LLA) compatibilizes the phase separated structure of PCL domains in PLLA matrix. The size of PCL domains in PLLA matrix became much smaller than that in a solution blended sample. The average sizes of PCL domains are controllable in the level of sub-micron scale.