UV grafting: surface modification of cellulose nanofibers without the use of organic solvents†
Polymer grafting provides cellulose nanofibers (CNFs) with new features. However, the process of polymer grafting, which generally involves a large amount of organic solvent, is environmentally unfriendly. We irradiated an aqueous suspension of CNFs with ultraviolet (UV) light to generate radicals on the surfaces of the CNFs, initiating polymer grafting. As a result, poly(methyl methacrylate) (PMMA) was readily grafted from the CNFs, without destroying the crystalline region of cellulose. PMMA-grafted CNFs have a unique nanofiber-nanoparticle structure in water, and show improved hydrophobicity and redispersibility in organic solvent. As well as PMMA, various other polymers can be grafted from CNFs without using organic solvents. We believe that this technique, called UV grafting, may provide a greener method for producing CNF materials with novel features.