Controlling Structure and Rheology of Cellulose Nanofibril Colloidal Gels at Low Volume Fractions

High Resolution Image Download MS PowerPoint Slide Cellulose nanofibrillar (CNF) gels, formed at very low volume fractions of solids, provide model systems for studying structure–property relationships in fibrillar colloidal networks. However, their properties depend not only on fibril characteristics but also on the liquid phase within the network. Here, we investigate how different liquids, with distinct properties, affect fibril–fibril interactions and how this change alters the network microstructure and mechanical properties of carboxymethylated CNF gels at very low volume fraction. Small-angle X-ray scattering showed a gradual transition from a clustered, heterogeneous network in the hydrogel toward a more homogeneous, dense structure upon liquid exchange. Rheological evaluations revealed an increase in the storage modulus and a decrease in the critical strain in liquid-exchanged gels, suggesting a stiffer, but more brittle, structure when using liquids of lower dielectric constant. Rheological modeling further distinguishes elastic, viscous, and yielding responses under applied stress. Together, these findings show how liquid-mediated changes in fibril interactions control CNF network organization and mechanical performance of the gels, offering design insights for tuning soft colloidal materials of nanosized anisotropic particles.