Nanocellulose Networks: Utilizing Colloidal Processing Principles to Tune The Mechanical Properties of Solid Foams

In recent years, nanocellulose has emerged as a sustainable and environmentally friendly alternative to traditional petroleum-derived structural polymers. However, the widespread implementation of nanocellulose is hindered by high energy-intensive extraction and processing methods, limited quality reliability, and cost-effectiveness<b> [1]</b>. In addition, the required fundamental understanding of process parameters that govern the morphology and structure-property relationships of nanocellulose systems, from colloidal suspensions to bulk materials, has not been developed and generalized for all forms of cellulose. This further hinders the more widespread adoption of this biopolymer in applications.<br/>In this study, we explore the tunability of mechanical properties of cellulose bulk structures, by investigating the intricate connections between thermodynamic, electrokinetic, and hydrodynamic interactions in nanocellulose networks, within the context of stability, phase transformations, and their profound impact on enhancing the properties of bulk materials. To delve into thermodynamic interactions, we examine different concentrations of various nanocellulose-solvent pairs with varying Flory-Huggins interaction parameters. Electrokinetic interactions are explored by manipulating surface charge densities, while hydrodynamic interactions are studied through concentration-based transitions. The interplay between thermodynamic and electrokinetic stability is elucidated through time-series polarized light and cross-polarized light imaging of the nanocellulose colloids. We employ Dynamic Light Scattering (DLS) to assess the Fuchs Stability Ratio and correlate the Diffusion Limited Cluster Aggregation (DLCA) and Reaction Limited Cluster Aggregation (RLCA) regimes<b>[2]</b> with the rheological properties of the colloids. This sheds light on the underlying mechanisms and the specific interactions responsible for the concentration-based Onsager's Isotropic to Nematic phase transition, and in addition, enables a co-relation of the properties at the colloidal state <b>[3]</b> and the final solid structures. Small-angle X-ray scattering (SAXS) is employed to comprehensively understand the influence of various processing parameters on the ordering of the final bulk structure and, subsequently, the structure-property relationships. Our study enriches the understanding of nanocellulose processing from a polymer physics and colloidal chemistry perspective. These findings hold the potential for extending to multicomponent biomass-based systems in the future, contributing to sustainable and high-performance materials development.<br/><br/><br/><b>1.</b> Dileswar Pradhan, Amit K. Jaiswal, Swarna Jaiswal, “Emerging technologies for the production of nanocellulose from lignocellulosic biomass”, Carbohydrate Polymers, Volume 285,2022,119258, ISSN 0144-8617, https://doi.org/10.1016/j.carbpol.2022.119258.<br/><b>2.</b> M. Mellema, J. H. J. van Opheusden, T. van Vliet; Relating colloidal particle interactions to gel structure using Brownian dynamics simulations and the Fuchs stability ratio. J. Chem. Phys. 1 October 1999; 111 (13): 6129–6135. https://doi.org/10.1063/1.479956<br/><b>3.</b> Benselfelt, T., Kummer, N., Nordenström, M., Fall, A. B., Nyström, G., & Wågberg, L, The Colloidal Properties of Nanocellulose,ChemSusChem,https://doi.org/10.1002/cssc.202201955