Dual cross-linked cellulose based hydrogel films†

Abstract

Polymeric hydrogels and the associated structural assemblies are endowed with exceptional capabilities for applications in biomedicine, chemical biology, molecular electronics and wider energy paradigm. Cross-linking chemistry adds extra handles to tailor the gelation process and functional properties, surpassing those of traditional hydrogels. Here, we present molecularly tethered gelation of a cellulose (C) derivative by taking advantage of covalent and non-covalent interactions using organic and ionic linkers, respectively. The dual-cross-linked C-based hydrogels can be synthesized at a moderate temperature (∼70 °C) and processed into thin films using a programmable dip-coater at room temperature. The hydrogel films exhibited enhanced pH stability compared to the mono-cross-linked gels, were long-lived (over 180 days) and showed excellent ion-exchange properties. The gelation mechanism, local structures, and ion-exchange properties were corroborated by high-field (28.2 T, ¹H = 1200 MHz) solid-state NMR spectroscopy. A facile gelation process enabled by covalent linkages, metal coordination, and multimodal characterization demonstrated here is expected to provide opportunities for a number of unexplored applications.