Synthesis and two-dimensional ordering of asymmetrically polymer–brush–decorated cellulose nanocrystals

Rod-shaped cellulose nanocrystals (CNCs) are typically obtained by hydrolyzing cellulose nanofibers bearing an formyl group at their reducing end. In this study, we prepare CNCs bearing densely grafted polymer brushes of different molecular weights (asymmetrically polymer-brush–decorated CNCs; aPB-CNCs). aPB-CNCs exhibit good dispersion in organic solvents and form a monolayer at the air/water interface. The compression of this monolayer induces a phase transition of a long polymer brush at the reducing end and a change in the orientation of the CNC core due to repulsive interactions. A CNC is identified as a key intermediate, possessing dormant moieties for reversible addition–fragmentation polymerization and atom transfer radical polymerization at the reducing end and other surfaces, respectively (bifunctional dormant CNC). This functional CNC facilitates the polymerization of a wide range of monomers and enables the synthesis of aPB-CNCs with diverse chemical properties. The developed synthetic route not only provides a basis for exploring the ordered structure of nanoparticles but is also useful for modifying the reducing ends of CNCs. Cellulose nanocrystals (CNCs) bearing densely grafted polymer brushes of different molecular weights (asymmetrically polymer-brush–decorated CNCs; aPB-CNCs) were synthesized via a CNC intermediate possessing two types of dormant moieties for controlled radical polymerization at the reducing end and other surfaces, respectively. The aPB-CNCs exhibited good dispersion in organic solvents and form a monolayer at the air/water interface. The compression of this monolayer induced a phase transition of a long polymer brush at the reducing end and a change in the orientation of the CNC core due to repulsive interactions.