Nanofibrillar networks and superstructuring of cellulose nanocrystals and nanofibers: A basis for universal adhesion

B.D. Mattos, B.L. Tardy, L.G. Greca, T. Kämäräinen, W. Xiang, O.J. Rojas
University of British Columbia,
Canada

Keywords: nanofibrillar networks, nanocrystals

Summary:

In this talk we will discuss the role of nanonetworks formed by cellulose nanofibrils (CNF), which enable superstructuring of a large variety of particle types for a wide range of applications. An intermixed network of fibrils with particles increases the toughness of related assemblies by up to three orders of magnitude compared, for instance, to sintering. Supramolecular cohesion is transferred from the fibrils to the constructs following a power law. Our findings apply to other fibril dimensions, including those associated with cellulose microfibrils. Similar principles apply to water-based adhesives obtained from cellulose nanocrystals (CNC). Here, a bottom-up approach to adhering solid surfaces is produced by evaporation-induced self-assembly (EISA) of CNC. The high strength CNCs pack into structures in the form of rigid concentric rings within which a highly ordered nematic arrangement is observed. The multi-scaled long-range order arising from the CNCs provides unprecedented adherence and tensile strength in-plane for self-assembled nanoparticles and only weak adhesion out-of-plane. Thus, superstructuring by the colloidal self-assembly of building blocks such as CNC and CNF is presented as a new paradigm to generate outstanding adhesion between solid surfaces. The prospects for scale-up efforts in these directions are discussed. References: Tardy B.L., Richardson J.J., Greca L.G., Guo J., Ejima H., Rojas O.J., Exploiting supramolecular interactions from polymeric colloids for strong anisotropic adhesion between solid surfaces, Advanced Materials, 1906886 (2020). DOI: 10.1002/adma.201906886 Mattos B.D., Tardy B.L., Greca L.G., Kämäräinen T., Xiang W., Cusola O., Magalhães W.L.E., Rojas O.J., Nanofibrillar networks enable universal assembly of superstructured particle constructs, Science Advances, Accepted (2020).