On the Formation Mechanism of Nonsolvent-Induced Porous Polylactide Electrospun Fibers

Polylactide (PLA) fibers were electrospun from the solutions of PLA dissolved in the mixtures of its good and poor solvents, and the formation mechanism of the poor solvent-induced porous structure on the fibers was investigated. From a systematic study using the pairs of a variety of good/poor solvents for electrospinning, the conditions, specifically the solvent properties, for producing uniform fibers with controllable pores that appear not only on the surface but also throughout the fibers were proposed. The water miscibility of the good/poor solvents is crucial, which is because the ambient moisture that condenses during electrospinning plays an important role in the formation of the pores. Furthermore, the evaporation rate of the good/poor solvents is another key factor that affects the pore size and pore distribution on fibers because the solvent evaporation rate regulates the moisture condensation and the phase-separated scale that are closely related to fiber morphology. The principles generalized in this work can be applied to other low-polar polymers for controlling the porosity of fibers. In addition, this work demonstrates that the porous PLA fibers can be electrospun from low-toxic solvents and that with a large surface area and storage space provided by the pores, the PLA porous fibers are highly capable of adsorbing oils, with a capacity double that of the smooth counterpart.