Regenerated Cellulose Microgel: A Promising Reinforcing Agent and Gelator for Soft Matter

Abstract

Unlike one-dimensional (1D) cellulose materials, such as cellulose nanofibers (CNFs), cellulose nanowhiskers, or microfibrillated cellulose, three-dimensional (3D) cellulose microgels have a multiscale structure composed of microscale particle size and nanoscale porous network. The hydrophilicity and microscale particle size enable homogeneous dispersion of microgels in water and render unique rheology property. While the nanoporous network of microgels assembled by the cellulose nanofiber allows diffusion and in situ polymerization of small molecules to form interpenetrating polymer network. Therefore, there is a huge potential for cellulose microgels as reinforcing agent and gelator for soft matter. In this work, as a proof of concept, cellulose microhydrogels (CMH) with narrow particle size distribution and tunable microstructure are prepared by applying high-speed shearing to chemically cross-linked regenerated cellulose macrogel. The as prepared microgels can be homogeneously dispersed in water, and form interpenetrating network with in situ polymerized polyacrylamide (PAM). This interpenetrating behavior between microgels and PAM accelerates the gelation process. Compared to CNFs reinforced PAM hydrogel, CMH/PAM hydrogel shows superior toughness in the compressive test with tunable mechanical properties by adjusting microstructure of microgel through tuning the cross-linking density. Cellulose microgel shows as a promising reinforcing agent and gelator for potential use in 3D printing of soft matter or as rheological modifier.