Effect of Precursor Solvent on the Occurrence of Stereocomplex Crystallization in Electrospun Polylactide Fibers

We conducted electrospinning to fabricate poly( l ‐lactide) (PLLA)/poly( d ‐lactide) (PDLA) fibers from chloroform (CF)/pyridine and CF/2,2,2‐trifluoroethanol (TFE) solutions. The effects of the electrospinning solvent and spatial confinement on the stereocomplex crystallization of the electrospun fibers were investigated. Thermal treatment of PLLA/PDLA fibers prepared using CF/pyridine resulted in the coexistence of homocrystals (HCs) and stereocomplex crystals (SCs), with SCs being predominant. This phenomenon was attributable to the uniform dispersion of polymer chains in CF/pyridine, which reduced chiral complementary pairing, resulting in the formation of HCs and SCs. By contrast, dissolving PLLA/PDLA in CF/TFE caused the pairing of PLLA and PDLA chains. Electrospinning with CF/TFE facilitated stereocomplexation, leading to the development of SCs. The degree of confinement did not affect the occurrence of stereocomplexation. However, fibers with a larger diameter provided a larger internal space for chain movement, resulting in a larger number of crystal nuclei. Thus, the crystallite size decreased but the crystallinity increased. The crystal development in small‐diameter fibers was strongly confined, which reduced the crystallinity but increased the crystallite size. The findings of this study can be used as a reference for controlling stereocomplex crystallization and fabricating fibers with desirable properties.