Reactive spinning to achieve nanocomposite gel fibers: from monomer to fiber dynamically with enhanced anisotropy†
Based on the analysis of time-consuming gelation mechanisms and excellent physical elongations of nanocomposite hydrogels (NC gels), pre-gel, which is an intermediate phase between precursor and hydrogel during the propagation of the polymer chain and gradual formation of cross-linked structures, has been found to display great reactive spinning potential. Then, a facile reactive spinning is presented for scalable fabrication of nanocomposite gel fibers (NC-GFs) from pre-gel by combining with an additional post-drawing process during gelation of the precursor solutions. The reactive kinetics of the hybrid precursor are monitored to offer precise temporal control of the phase transition regions from sol to pre-gel. At a specific time region after the critical gelation point (CGP), the formed pre-gel exhibited excellent stretchable property for sustaining subsequent physical post-drawing, and then could be continuously collected to obtain NC-GFs. The imposed post-drawing on the pre-gel not only exerted control over the diameter of the NC-GFs, but also induced evolution of an oriented structure of clay–polymer microdomain along the stretching direction, resulting in high anisotropy and enhanced mechanical performance of the NC-GFs. Besides, utilizing the non-crystallizable glycerol/H2O as a co-solvent, such NC-GFs displayed improved long-term practicality, including outstanding stable mechanical performance, as well as anti-freezing property (−20 °C).