Modulation of Assembly and Dynamics in Colloidal Hydrogels via Ionic Bridge from Cellulose Nanofibrils and Poly(ethylene glycol).

The biologically inspired dynamic materials offer principles for designing man-made systems by using assembly approach. In this work, the hybrid hydrogels consist of cellulose nanofibrils (CNFs) that combine a mechanically strong skeleton with flexible PEG chains. The distinct gel state is observed at room temperature with ' > ″ and an order of magnitude higher ' values from 0.08 to 0.93 kPa upon increasing CNF concentration from 0.2 to 2 wt % at constant 2 wt % PEG. Combined with mechanically strong CNFs and dynamic ionic bridges through amine-terminated tetra-arm PEG adsorption to TEMPO-oxidized colloidal nanofibrils surface, the assembled colloidal hydrogels show high modulus, reversible gel-sol transition, and rapid self-recovery properties. It is envisioned that simply mixing hard CNF and soft polymeric matrix would lead to a facile method to bridge reversible dynamic bonds in a cellulose-based hybrid network and broad cellulose applications in the preparation of high performance supramolecular systems.