Competitive Crystallization Mechanisms in Enantiomeric PLA/DMF Systems: Toward Tailored Porous Morphologies

Poly(lactic acid) (PLA) porous materials hold great promise for biomedical applications such as tissue engineering and drug delivery. However, achieving precise control over their pore architecture remains challenging due to the complex interplay between phase separation and crystallization. This study investigates the temperature-directed competition among cocrystallization, homocrystallization, and stereocomplex (SC) crystallization in PLA/dimethylformamide (DMF) systems during thermally induced phase separation (TIPS). By quenching PLLA/PDLA solutions with varying ratios over a wide temperature range (−20 to 30 °C), we demonstrate that the final morphology, which ranges from three-dimensional nanofibrous networks to well-ordered lamellae or monodisperse microspheres, is intricately governed by the dominant crystallization pathway. At lower temperatures, the formation of PLA–DMF ε-complex crystals templates a nanofibrous structure upon solvent removal. In contrast, at elevated temperatures, SC crystallization is exclusively promoted in equimolar blends, resulting in coarse spherical particulates. Furthermore, the morphology and microstructure are found to influence the thermal stability and enzymatic hydrolysis rate of the PLA porous materials, without inducing cytotoxicity. These findings provide deeper insight into the crystallization-phase separation interplay in PLA systems and establish a versatile strategy for fabricating PLA-based materials with tailored morphologies to meet specific biomedical requirements.