Speaker
Description
Poly(lactic acid) (PLA) is a widely used bio-based polymer due to its renewable origin, biodegradability, and versatility across packaging, biomedical, and additive manufacturing applications. Poly(lactic acid) (PLA) is an extremely attractive material due to its unique crystallization versatility: it can crystallize not only in the homopolymeric form from poly(L-lactic acid) (PLLA) or poly(D-lactic acid) (PDLA), but also as stereocomplex (SC) crystals through the association of enantiomeric PLLA and PDLA chains [1]. This dual crystallization capability enables access to crystalline structures with distinct and tunable thermal and mechanical properties, broadening the range of potential applications for PLA. Stereocomplex crystals exhibit tighter chain packing and significantly higher melting temperatures, resulting in improved thermal stability, mechanical strength, and long-term durability. Despite their promising properties, current stereocomplex production methods—primarily melt processing and solution casting—offer limited control over crystal purity, spatial localiza- tion, and reproducibility. High processing temperatures, complex thermal histories, and bulk crystallization often lead to the coexistence of stereocomplex and homochiral crystals, while preventing direct observation of stereocomplex nucleation and growth. In this work, we develop a continuous, solution-based microfluidic platform with a Y-junction geometry for the controlled production of PLA stereocomplex crystals at room temperature. Enantiomer-pure PLLA and PDLA solutions in chloroform are combined under well-defined flow conditions, enabling precise control over residence time and mass transport. By exploiting the markedly lower solubility and higher thermodynamic stability of PLA stereocomplex crystals in chloroform compared to homochiral α-form PLA [2], stereocomplexation is selectively favored while competing homocrystallization is suppressed. We demonstrate that increasing the resi- dence time systematically enhances the stereocomplex fraction at the outlet. Rational device design guided by diffusion and crystallization timescales further enables tunable control over stereocomplex formation and productivity under continuous flow. The output materials are quantitatively characterized using X-ray scattering techniques and differential scanning calorimetry (DSC), allowing precise determination of crystalline structure, stereocomplex content, and thermal properties. In addition, the transparent microfluidic platform provides direct optical access to the region where the enantiomeric solutions interact, enabling real-time observation by optical and polarized light microscopy. Overall, this study introduces a novel, continuous microscale strategy for PLA stereocomplex production and provides new insights into stereocomplexation kinetics under well-defined, non- equilibrium conditions, paving the way for scalable manufacturing of high-performance, fully bio-based polymer materials.
[1] Yoshito Ikada, Khosrow Jamshidi, Hideto Tsuji, and Suong Hyu Hyon. Stereocomplex formation between enantiomeric poly(lactides). Macromolecules, 20(4):904–906, 7 2002. ISSN 15205835. doi: 10.1021/MA00170A034.
[2] Hideto Tsuji, Fumitaka Horii, Suong Hyu Hyon, and Yoshito Ikada. Stereocomplex formation between enantiomeric poly(lactic acid)s. 2. Stereocomplex formation in concentrated solutions. Macromolecules, 24(10):2719–2724, 5 2002. ISSN 15205835. doi: 10.1021/MA00010A013.