Douliez Jean-Paul, Navailles Laurence, Nallet Frédéric
Equipe Interfaces et Systèmes Dispersés, BIA, INRA, rue de la Géraudière, F-44316 Nantes, France.
Langmuir. 2006 Jan 17;22(2):622-7. doi: 10.1021/la052377u.
Long-chain fatty acids are insoluble in aqueous solution and form crystal precipitates. It is then of particular importance to determine the physicochemical parameters allowing their dispersion in water to improve their bioavailability and their utilization as surfactants. Herein, we report a study on salt-free catanionic systems in aqueous solution made of mixtures between palmitic or stearic fatty acids and alkylboladiamines (Abd's) differing by their alkyl chain length. Phase contrast microscopy, solid-state NMR, Fourier transform infrared spectroscopy, and small-angle neutron scattering were used to characterize the phase behavior of these systems at molar ratio of fatty acid to Abd of 1 and 2. Whatever the Abd and the molar ratio, fatty acids were embedded at low temperature in a bilayer gel phase which crystallizes after a period of rest. At an equimolar ratio, the gel phases transited upon raising the temperature to an isotropic phase made of worm-like micelles except in the case of the ethylenediamine chain for which a lamellar fluid phase was observed. At a molar ratio of 2 and high temperature, fatty acids were embedded in a lamellar fluid phase which self-orients with its stacking axis perpendicular to the magnetic field. However, for a long alkylboladiamine such as spermine, worm-like micelles formed. The phase behavior at high temperature is discussed in terms of molecular volume.
长链脂肪酸不溶于水溶液并形成晶体沉淀。因此，确定能够使其在水中分散以提高其生物利用度及其作为表面活性剂的利用率的物理化学参数尤为重要。在此，我们报告了一项关于由棕榈酸或硬脂酸与烷基双胺（Abd's）混合而成的无盐水溶液中的阴阳离子体系的研究，这些烷基双胺的烷基链长度不同。利用相差显微镜、固态核磁共振、傅里叶变换红外光谱和小角中子散射来表征这些体系在脂肪酸与Abd的摩尔比为1和2时的相行为。无论Abd和摩尔比如何，脂肪酸在低温下都嵌入双层凝胶相中，经过一段时间的静置后会结晶。在等摩尔比下，除了观察到层状流体相的乙二胺链的情况外，随着温度升高，凝胶相转变为由蠕虫状胶束组成的各向同性相。在摩尔比为2且温度较高时，脂肪酸嵌入层状流体相中，其堆积轴垂直于磁场自我取向。然而，对于像精胺这样的长烷基双胺，会形成蠕虫状胶束。从分子体积的角度讨论了高温下的相行为。
