Tanaka Keisuke, Hirai Yuki, Suzuki Toshiyuki, Akamatsu Masaaki, Sakai Kenichi, Sakai Hideki
NIKKOL GROUP Cosmos Technical Center Co., Ltd.
Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science.
J Oleo Sci. 2019 Mar 1;68(3):225-231. doi: 10.5650/jos.ess18211. Epub 2019 Feb 13.
Monohexadecyl phosphate, neutralized by L-arginine (C16MP-Arg), forms an α-gel (α-type hydrated crystal) with water. In this study, we characterized the behavior of water in the C16MP-Arg α-gel system by means of small/wide angle X-ray scattering (SWAXS), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and H nuclear magnetic resonance (NMR) spectroscopy. An increased water concentration resulted in an increase in the d-spacing of the lamellar bilayers as well as an increased wavenumber for the O-H stretching vibration peak. In addition, the melting enthalpy increased with increasing water concentration, while freezing was not observed below a water concentration of 20 wt%. These results suggest that the overall properties of water changed as a function of its concentration in the sample. H-NMR spin-spin relaxation time (T) measurements further suggest that the protons of water and C16MP-Arg can be classified into three components (low-, middle-, and high-T components) as a function of the temperature and concentration. The low-T component mainly arose from the protons of C16MP-Arg alkyl chains, and its mobility increased with increasing temperature. The high-T component arose from the protons of water. The water behaved as "bound water" for the C16MP-Arg headgroups at -30°C and a water concentration of 20 wt%, and the mobility increased with increasing temperature and water concentration. These changes suggest that an increased water concentration results in an increased amount of water being incorporated between the C16MP-Arg lamellar bilayers as well as in spaces surrounded by α-gel domains.
由L-精氨酸中和的单十六烷基磷酸酯（C16MP-Arg）与水形成α-凝胶（α型水合晶体）。在本研究中，我们通过小角/广角X射线散射（SWAXS）、傅里叶变换红外光谱（FT-IR）、差示扫描量热法（DSC）和氢核磁共振（NMR）光谱对C16MP-Argα-凝胶体系中的水行为进行了表征。水浓度的增加导致层状双分子层的d间距增加，同时O-H伸缩振动峰的波数也增加。此外，熔化焓随水浓度的增加而增加，而在水浓度低于20 wt%时未观察到冻结现象。这些结果表明，水的整体性质随其在样品中的浓度而变化。H-NMR自旋-自旋弛豫时间（T）测量进一步表明，水和C16MP-Arg的质子可根据温度和浓度分为三个组分（低、中、高T组分）。低T组分主要来自C16MP-Arg烷基链的质子，其迁移率随温度升高而增加。高T组分来自水的质子。在-30°C和20 wt%的水浓度下，水对于C16MP-Arg头基表现为“结合水”，并且迁移率随温度和水浓度的增加而增加。这些变化表明，水浓度的增加导致C16MP-Arg层状双分子层之间以及α-凝胶域包围的空间中结合的水量增加。
