Hybrid Materials from Cellulose Nanofibrils and Charged Core-Shell Nanolatexes

Cellulose nanofibrils (CNFs) are one of the most promising lignocellulosic feedstocks for the design of sustainable and advanced materials to meet the challenges of the future. CNFs are produced as aqueous colloidal dispersions of fibrils with diameters of a few nanometers and aspect ratios of several hundred. These dispersions can be dewatered in different processes to give foams, membranes, nanopapers, and nano-reinforcements, to name a few. The mechanisms for dewatering, and the impact of additives upon the assembly of nanofibrils, remains a challenging topic with great potential for tailoring the material to new properties and applications.<br/>The exploration of core-shell polymeric nanolatexes as CNF additives is still just in its infancy. In this project we combine CNFs with a nanolatex synthesized through reversible addition−fragmentation chain-transfer (RAFT)-mediated polymerization-induced self-assembly (PISA) in water. The PISA process makes for a flexible platform in the synthesis of functional nanolatex with tunable size, surface charge and functionality. These nanoparticles have already shown great promise as compatibilizers when adsorbed to CNFs [1], and early work has indicated the introduction of interesting mechanical behavior to CNF materials [2].<br/>In this project we investigate structures formed between anionic CNFs and small additives of a cationic nanolatex. We look at the impact of nanolatex charge and size as nanolatex is adsorbed to CNFs in dispersion and dewatered to give hybrid structures. The addition of nanolatex affects the mechanical properties, water sensitivity and response to heat treatment of these materials. The current work is an indication that nanolatexes can act as efficient compatibilisers for CNF networks, and that these hybrid structures deserve further systematic investigation.<br/><br/>[1] Alexakis, A. E., et al. (2021). "Modification of cellulose through physisorption of cationic bio-based nanolatexes – comparing emulsion polymerization and RAFT-mediated polymerization-induced self-assembly." Green Chemistry.<br/>[2] Engström, J., et al. (2017). "Soft and rigid core latex nanoparticles prepared by RAFT-mediated surfactant-free emulsion polymerization for cellulose modification – a comparative study." Polymer Chemistry 8(6): 1061-1073.