Visualizing Crystallization and Phase‐Separated Morphology in PBAT / PLA Blends Using an AIE Fluorescent Probe

ABSTRACT Amino‐modified tetraphenylethylene (TPE), an aggregation‐induced emission (AIE) fluorescent probe, was employed to investigate crystallization and phase separation of thermodynamically immiscible biodegradable poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blends, whose interfacial and crystalline structures govern macroscopic properties but are hard to visualize via conventional methods. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD) reveal that flexible PBAT segments enhance PLA chain mobility and crystallinity, whereas TPE restricts chain motion of both components and suppresses crystallization in neat homopolymers and their blends. Fluorescence microscopy confirms TPE preferentially accumulates in the PLA phase and enriches at the PLA/PBAT interface to form an interphase, enabling direct visualization of phase separation morphology. Thermogravimetric analysis (TGA) shows TPE reduces polyester chain entanglement and lowers the maximum thermal decomposition temperature of both phases. Scanning electron microscopy (SEM) of tensile‐fractured surfaces indicates interfacially enriched TPE reduces interfacial tension and improves adhesion, but inhibits the debonding‐cavitation toughening mechanism, decreasing tensile strength and elongation at break. Fluorescence intensity positively correlates with blend crystallinity, as rigid crystalline regions confine TPE intramolecular rotation. This work provides an intuitive in situ visualization strategy for correlating interfacial structure, crystallization and, performance of biodegradable polyester blends via AIE probes.