Fiber forming mechanism and reaction kinetics of novel dynamic-crosslinking-spinning for Poly(ethylene glycol) diacrylate fiber fabrication

Abstract One dimensional hydrogel fibers have been considered as new types of prospective fiber materials in biomedical and intelligence applications. However, continuous fabrication of hydrogel fibers is still challenging. Based on the successful establishment of a facile dynamic-crosslinking-spinning (DCS) strategy to produce hydrogel microfibers on a large scale from poly (ethylene glycol) diacrylate (PEGDA) oligomer we demonstrated before, herein, we systematically investigated the fiber forming mechanism and the reaction kinetics involved in the DCS process. We found out that the PEGDA oligomer composed newtonian fluid spinning solution could form a continuous and stable fiber-shaped solution stream after vertical extrusion due to the skillfully taking advantage of gravity to counteract the disturbance from the drawing force. Subsequently, the extruded PEGDA stream could be polymerized dynamically by in-situ photopolymerization to form a continuous PEGDA hydrogel fiber. The double bond conversion of oligomer was positively linear related to the PEGDA concentration, UV intensity, photoinitiator concentration, and negatively determined by the winding speed, which was according to the reaction kinetics of the acrylate in air. Moreover, the surface roughness of fiber induced by self-swelling was also related to double bond conversion in DCS method. Incomplete polymerization could be improved by additional thermal post-treatment, which was applicable for the enhancement of the mechanical properties of fiber due to the improved crosslinking density.