Cyclic compounds such as lactones and N-carboxy α-amino acid anhydrides (NCAs) were graft-polymerized on cellulose dissolved in tetrabutylammonium fluoride ⁄ dimethyl sulfoxide (TBAF ⁄ DMSO). ε-Caprolactone was grafted on cellulose with grafting of 64% in this solvent system. NCAs were also grafted with grafting of over 100%. It is thought that an increase in the nucleophilicity of hydroxyl groups of cellulose by the interaction with TBAF was related to this polymerization.