Journal
CARBOHYDRATE POLYMERS
Volume 92, Issue 2, Pages 1827-1834Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.carbpol.2012.11.043
Keywords
Konjac glucomannan; Triacetate; NMR; Thermal and mechanical properties
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Funding
- Japan Society for the Promotion of Science (JSPS) [22245026]
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Fully substituted glucomannan triacetate (GMTAc) (degree of substitution (DS) = 3.0) was prepared from konjac glucomannan (KGM) treated with acetic acid and trifluoroacetic anhydride (TFAA). The peaks in the H-1- and C-13 NMR spectra of GMTAc were assigned in detail based on two-dimensional (DQF-COSY, HSQC and HMBC) NMR analysis. Glucomannan acetate samples (GMAc) with different degrees of substitution (DS = 1.3, 1.7, 2.0 and 2.8) were prepared by partial deprotection of GMTAc. Thermal properties of GMAcs including GMTAc were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Their decomposition temperatures were higher than that of KGM, and increased with increase in DS. DSC measurements revealed that GMAc had a high glass transition temperature in the range of 178-219 degrees C, which decreased with increase in DS. The samples did not exhibit melting peaks, indicating that the GMAcs were amorphous. All GMAcs formed transparent films upon solvent casting, and tensile tests revealed that GMAc had a higher tensile strength and elongation to break at lower DS (1.3 and 1.7) compared to higher DS (2.0, 2.8 and 3.0). This means that the mechanical properties of GMAc could be controlled by DS. (C) 2012 Elsevier Ltd. All rights reserved.
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