Self-assembly of nanoparticles into macroscopic constructs, i.e. superstructuring, is a powerful framework to extend nano-scaled properties to the macroscopic scale. Superstructured colloidal materials exploit the synergies between components also to develop new or enhanced functions. Cohesion is a primary requirement for scaling-up such assemblies into bulk materials, but it has only been fulfilled in case specific bases. Thermal annealing and polymeric binder have been often applied to introduce interparticle bonding; however, such strategies either erase or modify the functionalities of the primary building blocks. The compositional dependence on the formation process is a major issue for scale-up efforts, and it expressively limits developments of new nanomanufactured materials. Here, we demonstrate that the complex topology of highly interconnected fibrillar networks formed by supramolecularly cohesive cellulose nanofibrils (CNFs) can be used as a cohesion-inductor co-component in particulated networks. The variety of fibrillar networks formed from CNF (from foams to aerogel-like) enables robust superstructuring with virtually any particle – broad rang of sizes and surface chemistries. An intermixed network of fibrils with particles increases the toughness of the assemblies by up to three orders of magnitude compared, for instance, to sintering. Using a variety of SPs, a numerical correlation between the relative surface area between particles and CNFs with the cohesion of the formed network was described. Supramolecular cohesion is transferred from the fibrils to the constructs following a power law, with a constant decay factor for particle sizes from 230 nm to 40 µm. The hierarchical architecture of the intermixed particle-fibril network, however, is strongly dependent on the surface potential of the particles. Hydrophobic building blocks intensify interfibril interactions, while positively charged particles favor strong interactions at the fibril-particle interface. Such behavior is also described by our scaling law for cohesion. These findings are applicable to other nanofiber dimensions via a rationalization of the morphological aspects of both particles and nanofibers. CNF-based cohesion will move developments of functional colloids from laboratory-scale towards their implementation in large-scale nanomanufacturing of bulk materials.

Nanofibrillar networks from cellulose biocolloids enable universal assembly of superstructured particle constructs

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.