Substituent distribution of propyl cellulose studied by nuclear magnetic resonance

• Published in: Carbohydrate research 2020-09, Vol.495, p.108067-108067, Article 108067
• Main Authors: Kono, Hiroyuki, Numata, Jun
• Format: Article
• Language: English
• Subjects: Cellulose derivative; NMR; Propyl cellulose; Substituent distribution
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2020.108067

A series of propyl cellulose (PC) samples with different degrees of substitution (DS) ranging from 0.34 to 2.02 were prepared by a slurry method using propyl bromide as the etherification reagent. Two-dimensional nuclear magnetic resonance (NMR) studies were performed to identify the 1H and 13C chemical shifts of eight anhydroglucose units (AGUs) in PC chains including un-, 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted ones. In addition, the mole fractions (χ) of these AGUs in the studied PC samples and their changes with DS were determined from the quantitative 13C NMR spectra. The obtained χ−DS profiles were different from those of methyl and ethyl celluloses prepared by a similar slurry method, indicating that the molecular sizes of the substituent reagents utilized for cellulose ethers strongly affected their substituent distributions. [Display omitted] •NMR chemical shifts of propylcellulose-containing monomers are identified.•Monomer mole fractions are quantified using 13C NMR line shapes.•Substituent group interactions are determined by studying chemical shift changes.•Monomer mole fractions depend on the chain lengths of substituent groups.