Akihiko Watanabe's research while affiliated with Kwansei Gakuin University and other places
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Publications (5)
Our recent IR study demonstrated that hydrogen-bond structure in cellulose Ibeta drastically changes around 220 degrees C (Watanabe et al. Biomacromolecules 2006, 7, 3164). In the present study, temperature-dependent IR spectra of cellulose Ialpha from 30 to 260 degrees C were analyzed by use of perturbation-correlation moving-window two-dimensiona...
Infrared (IR) spectra were measured for cellulose Ibeta prepared from the mantle of Halocynthia roretzi over a temperature range of 30-260 degrees C to explore the temperature-dependent changes in hydrogen bonds (H-bonds) in the crystal. Structural changes at the phase transition temperature of 220 degrees C are elucidated at the functional group l...
Molecular interactions between microcrystalline cellulose (MCC) and water were investigated by attenuated total reflection infrared (ATR/IR) spectroscopy. Moisture-content-dependent IR spectra during a drying process of wet MCC were measured. In order to distinguish overlapping O–H stretching bands arising from both cellulose and water, principal c...
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 spe...
Temperature-dependent structural changes in hydrogen bonds (H-bonds) in microcrystalline cellulose (MCC) were investigated by infrared (IR) and near-infrared (NIR) spectroscopy. The O–H stretching fundamentals and their first overtone bands were employed to explore the structural
changes. In order to analyze the overlapping OH bands due to various...
Citations
... Additionally, quercetin spectrum also exhibits some maxima typical of this compound, e.g., γOH stretching at 3100-3600 cm − 1 [37], γC=O stretching in aryl ketonic group at 1664 cm − 1 [38], γC=C stretching at 1610 cm − 1 and 1521 cm − 1 [38], σOH bending in plane of the phenol group at 1381 cm − 1 [38], σCH in plane bending in aromatic hydrocarbon at 1315 cm − 1 [38], γC ar -O stretching vibration of the phenolic groups (C ar -OH), C=C3-OH, and/or conjugated cyclic aryl-ether (C ar -OC) or vinyl-ether (=C(sp2)-OC) in the quercetin skeleton at 1262 cm − 1 [39][40][41], C-C(=O)-C stretching and bending in ketone at approx. 1160 cm − 1 [38], cyclic enolic form (=C(sp2)-OH) at 1014 cm − 1 in the heterocyclic ring of the flavon-3-ol (quercetin) [42], =C-H out of plane bending vibrations of the aromatic ring at 933 cm − 1 , 819 cm − 1 and 602 cm − 1 [38]. ...
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... Interactions between the -OH on a glucose unit of cellulose with other cellulose chains and with the -OH on the ricinoleic acid of castor oil, as depicted in Fig. 2a, may yield gelification. H-bonds gradually become weaker with increasing temperature (Watanabe et al. 2006), thereby enhancing the so-called shear banding phenomenon. ...
... The CST and FV indicate that the dosage of cellulose significantly limits the release of water from the sludge structure, even in comparison to raw sludge. The observed phenomenon may result from the hydrophilicity of cellulose, while the possible improvement in dewatering ability may result from the threedimensional structure of the cellulose solution forming a filter for solid particles [49,50]. ...
... Considering the FTIR spectrum in Figure 2 for the r-CAcF sample, based on the intensity of the FTIR band at 3468 cm −1 , this band can be assigned to OH groups with weak hydrogen bonds. On the other hand, the weak H-bonded OH groups probably appear in concert, mainly with structural changes in the intrachain hydrogen bonds [61]. The H-bonding energies can play a significant role in observable molecular rearrangements, which can be discussed through the apparent reaction mechanisms within the kinetic analysis. ...
... The hydrogen bonds are weaker in Iα than in Iβ. I's hydrogen bonds thermally break down at reduced temperatures, contributing to Iα reduced stability [58]. ...
