Improvement of physical and mechanical properties of electrospun poly(lactic acid) nanofibrous structures

Abstract

The electrospinning of stereocomplexed poly(lactic acid) (Sc-PLA) twisted yarns was our approach to produce PLA-based nanofibrous structures with improved physical and mechanical characteristics for the applications as medical devices. An electrospinning apparatus consisted of two nozzles, and a take-up/twister unit was employed to fabricate twisted yarns through a continuous procedure. The yarn samples were produced via electrospinning of the solutions of high molecular weights poly(d-lactide) (PDLA) and poly(l-lactide) (PLLA) and also their blend solution at 1:1 ratio, and their physical and mechanical properties were compared. The morphological studies indicated that uniform yarns composed of bead-free and smooth fibers were formed. Electrospinning of the blend solution of PLLA/PDLA resulted in developing fibers and yarns with smaller diameters. The DSC analysis showed that the Sc-PLA yarn had a higher melting peak (at 230 °C) compared to PLLA and PDLA samples (184 °C), indicating the formation of stereocomplex crystallites in this sample. After isothermal heat treatment, the formation of the stereocomplex crystals in the electrospun Sc-PLA yarn was also confirmed by FTIR and WAXD analyses. Furthermore, because of the formation of stereocomplex crystallites during the electrospinning process, the stress-at-break and Young’s modulus of the yarns were enhanced, while the strain-at-break (%) was reduced. The current approach of stereocomplexation during the electrospinning procedure, and simultaneously, collecting the stereocomplexed nanofibers in the form of twisted yarn, can improve the inherent lack of physical and mechanical features of PLA nanofibrous structures for advanced applications as medical textiles.