pH-Triggered Self-Assembly of Cellulose Oligomers with Gelatin into a Double-Network Hydrogel

Multicomponent systems for self-assembled molecular gels provide huge opportunities to generate collective or new functions that are not inherent in individual single-component gels. However, gelation tends to require careful and complicated procedures, because, among a myriad of kinetically trapped structures related to the degree of mixing of multiple components over a wide range of scales, from molecular level to macroscopic scale, a limited number of structures that exhibit the desired function need to be constructed. This study presents a simple method for the construction of double-network (DN) hydrogels with improved stiffness composed of crystalline cellulose oligomers and gelatin. The pH-triggered self-assembly of cellulose oligomers leads to the formation of robust networks composed of crystalline nanofibers in the presence of dissolved gelatin, followed by cooling to allow for the formation of soft gelatin networks. The resultant DN hydrogels exhibit improved stiffness; the improvement in gel stiffness with double networking is comparable to that of previously reported DN hydrogels produced via a time-consuming enzymatic reaction.