Miscibility and Isothermal Crystallization Behavior of Poly-(L-Lactide-Co-Glycolide)/ Poly(ρ-Dioxanone) Blends
We prepared a series of blends from solution co-precipitation of poly-(L-lactide-co-glycolide) (PLGA) and poly (ρ-dioxanone) (PPDO) at various mass ratios. Using a scanning electron microscopy (SEM), PLGA and PPDO were revealed to be immiscible. The crystallization behavior of PLGA/PPDO blends was investigated by differential scanning calorimetry (DSC) under isothermal conditions. Through comparing the crystallization exothermic peak location and the PLGA/PPDO blends' shape, the crystallization rate was determined to slow as the temperature increased. We applied the Avrami equation to analyze the primary stage of the isothermal crystallization and obtained relevant crystallization kinetic parameters. The data revealed that the PPDO component acted as nucleation sites in blends and accelerated the PLGA crystallization rate by increasing the crystallization rate constant k and decreasing the half-crystallization time (t1/2). The Arrhenius equation was used to analyze the crystallization's activation energy. Our analysis confirmed that blending with PPDO accelerates PLGA crystallization. Our micrograph imaging of the spherulites via a polarizing optical microscopy (POM) revealed that the PLGA/PPDO blends' crystals were smaller in size but greater in number than that of pure PLGA. This finding indicated that PPDO is a good nucleation agent for PLGA. All these results suggest that it is possible to control the PLGA crystallization rate by adding a PPDO component.