title: NMR characterization of methylcellulose: Chemical shift assignment and mole fraction of monomers in the polymer chains.
abstract: Methylcellulose samples with different degrees of substitution were prepared by a heterogeneous reaction of cellulose. Two-dimensional NMR spectroscopy provided complete assignment of the1H and13C chemical shifts of the un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted anhydroglucose units (AGUs). Comparative analysis of the chemical shift data revealed the relationship between the methyl substituents at the 2-, 3-, and 6-positions and the1H and13C chemical shifts of the AGUs; additivity could be applied to the1H and13C chemical shifts of methylcellulose. Quantitative13C NMR spectra of the samples determined the composition of the eight AGUs and the substituent distribution at the 2-, 3-, and 6-positions of cellulose. This provided estimations of the hydroxyl group reactivity toward methylation and the interactions between the substituent groups within the same AGU.
authors.affiliation: Division of Applied Chemistry and Biochemistry, National Institute of Technology, Tomakomai College, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan. Electronic address: kono@tomakomai-ct.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kono
authors.affiliation: Division of Applied Chemistry and Biochemistry, National Institute of Technology, Tomakomai College, Nishikioka 443, Tomakomai, Hokkaido 059 1275, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Fujita
authors.affiliation: Faculty of Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060 8628, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Tajima
keywords: Methylcellulose; Monomer composition; Nuclear magnetic resonance; Steric hindrance; Substituent distribution