Enhancing strength and toughness simultaneously: Diblock-grafted cellulose nanofiber one-component nanocomposites

To overcome the drawbacks of homopolymer-grafted CNF one-component nanocomposites, a range of diblock-grafted cellulose nanofiber (CNF), CNF-g-(polybutyl acrylate-b-polymethyl methacrylate)s were synthesized through reversible-deactivation radical polymerization (RDRP) methods. The chemical structures and ratios between the two blocks were confirmed, with surface-grafted CNF observed as submicron particles. Both thermal and thermodynamic analysis revealed two glass transition temperatures (T_g) in the diblock-grafted CNF, and phase-separated morphology was observed in the nanocomposites. The densely grafted CNF displayed island structures, while sparsely grafted samples transitioned into continuous structure. Thermodynamic analysis showed that the diblock-grafted CNF nanocomposites maintained mechanical properties at high temperatures. These nanocomposites demonstrated robust strength and toughnes, with tensile strength reaching as high as 43.7 ± 1.6 MPa and elongation at break of 70.3 ± 16.2 %. Moreover, while densely grafted CNF exhibited higher modulus and strength, whereas sparsely grafted CNF displayed behavior more reminiscent of thermoplastic elastomers, indicated by lower modulus and higher elongation.