Modification of the water-insoluble hemicelluloses via free radical copolymerization in diluted alkali aqueous medium

The synthesis of hemicelluloses-g-polyacrylamide (PAM) was carried out in diluted alkaline aqueous solution via free radical copolymerization initiated by redox initiator composed of potassium persulfate (KPS)/sodium thiosulfate (Na2S2O3). The less substituted hemicelluloses, l-arabino-4-O-methyl-d-glucurono-d-Xylan (wis-AGX), are the main components of the hemicelluloses isolated from corncobs by the ultrasound-assisted diluted alkali extraction method and exhibit poor water solubility, which largely limit their applications. The factors, such as the initiator dosage, the monomer concentration, and the reaction time, which influenced both the grafting percent and the grafting efficiency, were investigated. The chemical structure and thermal and macromolecular weight properties of the graft copolymers were characterized by Fourier transform infrared spectrometer (FT-IR), 1H nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The results indicated that the PAM moieties were successfully introduced into the side chains of the hemicelluloses, and the graft copolymers showed good solubility in water. Such modification is suggested to find a possible new way for broadening applications of water-insoluble hemicelluloses, and the resultant graft copolymers might have potential applications, such as gels, films, adsorbents, coatings, or drug delivery systems.