Non-isothermal crystallization kinetics and morphology of poly(3-hydroxybutyrate)/pluronic blends

Poly(3-hydroxybutyrate), PHB, was mixed with pluronic F68 or F127 to obtain polymer blends with increased hydrophilicity and thus suitable for biomedical applications. Blend films were obtained by thermomolding keeping the pluronic content <= 17 wt% to avoid immiscibility. The non-isothermal crystallization kinetics of the blends was investigated by both differential scanning calorimetry (DSC) and rheology. PHB and pluronics were found to be miscible in the melt with both pluronics acting as diluent. Polarized optical microscopy (POM) and X-ray scattering (SAXS, WAXS) revealed that blending increased the overall crystallinity, promoting crystal ordering through the formation of more resolved, ring-banded spherulites. However, the different diffusion rate of pluronic F68 and F127 led to a different segregation extent of pluronic in the extralamellar domains with different final morphological homogeneity. The mechanical properties of the blends intimately correlated with the structure at the nano and microscale.