Self-healing stimuli-responsive cellulose nanocrystal hydrogels.

A facile and universal approach to prepare cellulose nanocrystal reinforced functional hydrogels is proposed. An organic solvent-free and eco-friendly method was adopted, where both the modification and polymerization were conducted in an aqueous solution. Cellulose nanocrystal (CNC) and sodium alginate (SA) were first oxidized under mild conditions to introduce aldehyde groups. Subsequently, amine-containing vinyl functionalized monomers were introduced to the surface of CNC or backbone of oxidized SA via a dynamic Schiff-base reaction. The bio-based hydrogels were then prepared via a one-pot in-situ polymerization, where the functional CNC and SA served as novel macro-cross-linkers that contributed to the structural integrity and mechanical stability of the hydrogels. The hydrogels displayed uniform chemical and macroscopic structures and could self-heal within several hours at room temperature. The design of specific monomers will allow the introduction of stimuli-responsive properties to the functional hydrogels and a chemically robust thermally-triggered actuator was demonstrated. Due to its flexible design and practical approach, the hydrogels could find potential uses in agricultural and pharmaceutical products.