Crystallization and Segregation Behavior at the Submicrometer Scale of PCL/PEG Blends

The crystallization and segregation behavior of immiscible polycaprolactone/poly­(ethylene glycol) PCL/PEG (50/50) blends was investigated using mainly resonance-enhanced atomic force microcopy coupled with infrared spectroscopy (AFM-IR) which allows a spatial resolution of the order of 30–50 nm. Chemical infrared images of the blends at different scales highlight their island-like spherulitic structures. The nanoscale IR spectra on both sides of the spherulitic interfaces are different. The polymer segregation mechanism of the blend in the spherulitic structure is also investigated in which PEG is rejected outside of PCL spherulites at low crystallization temperature (30 °C) while it is rejected in the form of small nodules with a dimension in the order of few micrometers, inside of PCL spherulites at higher crystallization temperature (40 °C) due to the presence of an upper critical solution temperature (UCST).