Effect of Mixed Solvents on the Structure and Properties of PLLA/PDLA Electrospun Fibers

Abstract

The electrospinning of poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) microfiber membranes were carried out with dichloromethane (DCM), DCM/ethanol, DCM/acetone, DCM/hexane as the spinning solvent. Scanning electron microscope observation showed that the electrospun fiber obtained using DCM/ethanol (L/D-DE) mixed solvent was homogeneous without visible bead, which was better than any others. Moreover, plenty of pores could be found on the surface of the fibers obtained using the mixed solvents. The porous structure of fibers was significantly influenced by the ethanol (non-solvent) content. When the DCM/ethanol was 50:10 (v/v), the fibers were uniform and had isolated pores. XRD and DSC results indicated that the exclusive stereocomplex poly(lactide acid) (sc-PLA) crystallites without any homocrystallites poly(lactide acid) (hc-PLA) did form in all types of fibers. The crystallinity of sc-PLA in the L/D-DE fiber was higher than other samples due to the slowest evaporation rate. TGA test further indicated that the thermal stabilities of PLLA/PDLA electrospun fibers were slightly better than the PLLA. Furthermore, L/D-DE had the excellent mechanical properties and underwent the course of ductile fracture. Possible mechanisms accounting for the morphologies and tensile properties were also proposed in this study.