Electrospinning of polylactide (PLA) solutions produces coarse nanofibers mixed with numerous beads at the adopted conditions. Incorporation of ionic liquids with high conductivity in the solutions, however, promotes formation of fine PLA nanofibers with diameters of about 70 nm. It corresponds to significant stretching of the solutions as well as remarkable molecular alignment under the electrical field. As a result, high amount of mesophase besides a few crystals is induced in the fine PLA nanofibers. It is responsible for the accelerated cold crystallization above glass transition temperature. Notably, an enhancement in the melting point of about 10 degrees C is exhibited by the crystals transformed from the mesophase with remarkable molecular alignment in the fine PLA nanofibers. (C) 2015 Elsevier Ltd. All rights reserved.