V-Shaped amphiphilic polymer brushes grafted on cellulose nanocrystals: Synthesis, characterization and properties

Cellulose nanocrystals (CNCs) were modified using an amphiphilic triblock copolymer [poly(2-(dimethylamino) ethyl methacrylate)- b -poly(glycidyl methacrylate)- b -poly(2,2,3,4,4,4-hexafluorobutyl acrylate) (PDMAEMA- b -PGMA- b -PHFBA)] bearing epoxy functionalities located in middle segment of PGMA, which were used to react with the hydroxyl groups on the surface of the CNCs. The triblock copolymer was synthesized via a reversible addition fragmentation chain transfer (RAFT) polymerization reaction between 2-(dimethylamino) ethyl methacrylate, glycidyl methacrylate and 2,2,3,4,4,4-hexafluorobutyl acrylate, and characterized using 1 H-NMR spectroscopy and size exclusion chromatography (SEC). The successful modification of the CNCs was demonstrated by means of FT-IR, TGA , TEM , XRD and XPS . In addition, the surface properties of the modified CNCs were studied using water contact angle and surface tension studies. When compared with the pristine CNCs, the modified CNCs exhibited a higher contact angle and lower surface tension. Good dispersion of the modified CNCs was observed in different polar solvents, such as water, THF, DMF , CHCl 3 and toluene. The modified CNCs exhibited pH responsive properties, which were measured using dynamic light scattering (DLS). In addition, the stability of Pickering emulsions stabilized by PDMAEMA- g -CNC- g -PHFBA decreased with time or increasing pH. The droplet size increased gradually upon increasing the pH. This work provides a method to design sophisticated CNC-based materials, which benefit from both the intrinsic properties of the CNCs and the new characteristics conferred by the multifunctional grafted chains.