期刊
APPLIED SPECTROSCOPY
卷 60, 期 9, 页码 1054-1061出版社
SOC APPLIED SPECTROSCOPY
DOI: 10.1366/000370206778397452
关键词
two-dimensional correlation spectroscopy; 2DCOS; principal component analysis; PCA; cellulose; hydrogen bond; near-infrared spectroscopy; NIR spectroscopy; water adsorption; moisture content; OH stretching band
Water adsorption onto microcrystalline cellulose (MCC) in the moisture content (M-c) range of 0.2-13.4 wt % was investigated by near-infrared (NIR) spectroscopy. In order to distinguish heavily overlapping O-H stretching bands in the NIR region due to MCC and water, principal component analysis (PCA) and generalized two-dimensional correlation spectroscopy (2DCOS) were applied to the obtained spectra. The NIR spectra in four adsorption stages separated by PCA were analyzed by 2DCOS. For the low M-c range of 0.2-3.1 wt %, a decrease in the free or weakly hydrogen-bonded (H-bonded) MCC OH band, increases in the H-bonded MCC OH bands, and increases in the adsorbed water OH bands are observed. These results suggest that the inter- and intrachain H-bonds of MCC are formed by monomeric water molecule adsorption. In the M-c range of 3.8-7.1 wt %, spectral changes in the NIR spectra reveal that the aggregation of water molecules starts at the surface of MCC. For the high M-c range of 8.1-13.4 wt %, the NIR results suggest that the formation of bulk water occurs. It is revealed from the present study that approximately 3-7 wt % of adsorbed water is responsible for the stabilization of the H-bond network in MCC at the cellulose-water surface.
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