VISUALIZING MICELLIZATION OF PEG-B-PCL MULTIBLOCK COPOLYMERS IN PLA/PCL BLENDS USING AFM-IR

In our previous study, IR absorption mapping of two PEG-b-PCL (poly(ethylene glycol)-b-poly(ε-caprolactone)) multiblock copolymers with the same molar mass but different block sizes, incorporated at 1 and 5 wt% into PLA/PCL (poly(acid lactic)/poly(ε-caprolactone)) blends, was conducted using atomic force microscopy(AFM)-based infrared spectroscopy (AFM-IR). The incorporation was carried out in the molten state employing co-rotating twin-screw extrusion. The ability of the multiblock copolymers to micellize after leveling off the PLA/PCL interfacial tension depends on the molecular structure of the multiblock copolymer. Compatibilization with the shorter block-size copolymer resulted in non-self-organized preferential segregation into the PLA matrix, whereas the longer block-size copolymer achieved self-organization. PEG-b-PCL micelles, around 20 nm in diameter, negatively impact the overall mechanical properties of the blend, making the compatibilized PLA/PCL more brittle than pure PLA. However, compatibilization with shorter block-size multiblock copolymer effectively toughened PLA, increasing its elongation at break by more than four times compared to pure PLA.