Cellulose Nanocrystals Modified with Cationic Block Copolymers

Cellulose nanocrystals (CNC) offer unique mechanical and optical properties but face challenges that often prevent its commercial development, foremost its high hydrophilicity, which makes it incompatible with most polymers. Covalent polymer graft modification can address this issue; however, these processes are often complex and expensive. We present a simple, inexpensive route for the noncovalent modification of a CNC surface with block copolymers. Five new block copolymers, composed of a butyl vinyl imidazolium bromide anchoring (cationic) and a nonionic stabilizing block, were synthesized via nitroxide-mediated polymerization. The degree of polymerization (DPn) of the stabilizing and anchoring blocks was systematically varied. Dispersibility of modified CNC in various organic solvents was evaluated. It was found that the DPn of both the anchoring and stabilizing blocks has a significant impact on the amount of the polymer that can be noncovalently bound to the CNC surface as well as in dispersibility in various solvents.