Graft polymerization of 1,2-butylene oxide from cellulose in ionic liquid/N-methyl-2-pyrrolidone solvent

In this study, we investigated graft polymerization of an epoxide monomer, 1,2-butylene oxide (BO), from cellulose in an ionic liquid (1-butyl-3-methylimidazolium chloride (BMIMCl))/N-methyl-2-pyrrolidone (NMP) solvent. The cellulose solution was prepared by immersing a cellulose/BMIMCl solution in NMP. Cellulose in the resulting homogeneous solution was treated with sodium hydride to generate alkoxides, and the mixture was then heated in the presence of BO with stirring under desired conditions for progress of the ring-opening graft polymerization. The ¹H NMR and IR spectra of the isolated products suggested occurrence of the graft polymerization to produce polyether (poly(1,2-butylene oxide))-grafted celluloses. The degrees of polymerization of the graft chains were estimated after acetylation of their terminal hydroxy groups to be values up to 5.92, obtained by the reaction at 80 °C for 3 d. The X-ray diffraction results suggested that cellulose chains in the products did not form crystalline structure. The products with the shorter graft chains were soluble in higher polar organic solvents and partly soluble in moderate organic solvents. Solubility for the latter solvents was improved with increasing the graft chain lengths.