Adjusting Morphology, Structure, and Mechanical Properties of Electrospun High-Molecular-Weight Poly(l-Lactic-Acid) Nanofibrous Yarns Through Hot Stretching Treatment

An integrated strategy that combines innovative electrospinning technique with traditional hot-stretching post-treatment is designed and implemented to generate high-molecular-weight poly(l-lactic-acid) (hmwPLLA, Mw = 2 80 000 Da) electrospun nanofiber-constructed yarns (ENCYs). The internal fiber diameter within the hmwPLLA ENCYs is found to increase gradually with the increase of hmwPLLA solution concentration. The hmwPLLA ENCY generated from a concentration of 10% (w v-1) is demonstrated with uniform morphology with an average fiber diameter of 737.7 +/- 72.2 nm and an average yarn diameter of 454.9 +/- 3.5 mu m. Compared with the unstretched hmwPLLA ENCY, increasing the hot-stretching temperature can significantly enhance the fiber orientation and crystallinity. Moreover, the mechanical properties of stretched ENCYs are obviously enhanced compared with the unstretched control. The fiber orientation and crystallinity of stretched ENCYs are also found to be significantly improved with the increase of hot stretching rate, further resulting in the obvious increase of breaking strength and Young's modulus. Importantly, the braided textiles made from stretched hmwPLLA ENCYs exhibited great biocompatibility by effectively guiding the cell alignment and supporting the cell adhesion and proliferation. In summary, the high performance hmwPLLA ENCYs show great potential for the future design and development of advanced biomedical textiles.