A gelation mechanism depending on hydrogen bond formation in regioselectively substituted O-methylcelluloses

This paper discusses how the hydrophobic interactions as well as hydrogen bonds contribute to thermally reversible gelation of aqueous solutions for O-methylcellulose. The gelation behavior of a series of regioselectively substituted 2,3-di-O-methylcellulose (2,3MC-n: n = 1-3) differed from that for randomly substituted O-methylcellulose (R-MC). This was indicated by differential scanning calorimetry, near infrared spectroscopy (NIR) and small angle X-ray scattering. The formation of hydrogen bonds in 2,3MC-n and R-MC solutions was also determined by the curve fitting results of OH bands in NIR spectra. This method proved the presence of the intermolecular hydrogen bonds between the cellulosic samples and water. As a result, the gelation of the 2,3MC-n and R-MC solutions may be caused by cooperation of the hydrophobic interaction among methyl substituents with the intermolecular hydrogen bonds among hydroxyl groups at the C(6) position, which are dependent on the distribution of methyl groups. (C) 2003 Elsevier Science Ltd. All rights reserved.