Synthesis and Characterization of Cellulose-graft-poly(p-dioxanone) Copolymers via Homogeneous Ring-Opening Graft Polymerization in Ionic Liquids

Cellulose-graft-poly(p-dioxanone) copolymers (cellulose-g-PPDO) were homogeneously prepared via ring-opening graft polymerization (ROP) between p-dioxanone (PDO) and hydroxyl groups of cellulose using the catalyst 4-dimethylaminoptridine (DMAP) in the ionic liquid 1-butyl-3-methylimidazolium chloride (BmimCl). Chemical structures and physical properties of the cellulose-g-PPDO copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H, 13C, 1H-13C 2D heteronuclear single quantum correlation (HSQC)-NMR)), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques. By adjusting the reaction conditions, including the molar ratio of PDO to the anhydroglucose unit (AGU), amount of DMAP, and reaction temperature and time, the structure of the graft copolymers could be altered, and a series of copolymers with molar substitutions (MSs) in the range of 1.09 to 6.97 and polymerization degrees (DPs) varying from 1.85 to 2.88 were obtained. The graft copolymers exhibited a noticeably lower thermal stability than cellulose. After the attachment of PPDO groups, the crystalline structure of cellulose was disrupted because of the elimination of the inter- and intra-molecular hydrogen bonds of cellulose chains