A General Strategy to Electrospin Nanofibers with Ultrahigh Molecular Chain Orientation

Abstract

The degree of polymer chain orientation is a key structural parameter that determines the mechanical and physical properties of fibers. However, understanding and significantly tuning the orientation of fiber macromolecular chains remain elusive. Herein, we propose a novel electrospinning technique that can efficiently modulate molecular chain orientation by controlling the electric field. In contrast to the typical electrospinning method, this technique can piecewise control the electric field by applying high voltage to the metal ring instead of the needle. Benefiting from this change, a new electric field distribution can be realized, leading to a non-monotonic change in the drafting force. As a result, the macromolecular chain orientation of polyethylene oxide (PEO) nanofibers was significantly improved with a record-high infrared dichroic ratio. This was further confirmed by the sharp decrease in the PEO jet fineness of approximately 80% and the nanofiber diameter from 298 to 114 nm. Interestingly, the crystallinity can also be adjusted, with an obvious drop from 74.9% to 31.7%, which is different from the high crystallinity caused by oriented chains in common materials. This work guides a new perspective for the preparation of advanced electrospun nanofibers with optimal orientation–crystallinity properties, a merited feature for various applications.