Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302, India.
J Colloid Interface Sci. 2010 Apr 1;344(1):10-20. doi: 10.1016/j.jcis.2009.12.003. Epub 2009 Dec 6.
A new class of amphiphiles, N-(4-n-alkyloxybenzoyl)-L-alanine was designed and synthesized. These amphiphiles have been shown to form thermoreversible gels in organic solvents such as aromatic hydrocarbons, cyclohexane, and chlorinated hydrocarbons at room temperature. The effects of amide functionality, chain length of the hydrocarbon tail, and the chirality of the head group of the amphiphiles on the ability to promote gelation in organic solvents have been studied. The n-tetradecyl derivative showed the best gelation ability, whereas the amphiphile with DL-alanine as the head group formed weak organogels. The 4-dodecyloxybenzoic-1-carboxyethyl ester derivative in which the amide group is replaced by an ester group also formed weak organogels at a slightly lower temperature (293 K). The gelation number and the gel melting temperature of the gelators in different solvents were determined. The rheological measurements suggested that the organogels of n-tetradecyl derivatives are stronger than those of amphiphiles containing n-dodecyl chains. Also the organogels of the amphiphiles, except the one with an ester group, were found to have gel-to-sol transition temperatures, T(gs), higher than room temperature (approximately 303 K), which increased with the increase of chain length and total concentration of the gelator. SEM pictures of the gels show fibrous structures. Small-angle XRD and optical microscopy were also employed to characterize the gels. The organogels of alanine derivatives, except that of 4-dodecyloxybenzoic-1-carboxyethyl ester, showed optical birefringence. The mechanism of gelation was studied using (1)H NMR and FTIR spectroscopy. Hydrogen-bonding between -CO(2)H groups as well as pi-pi interactions were found to be important for the gelation process.
设计并合成了一类新型两亲分子 N-(4-正烷氧基苯甲酰基)-L-丙氨酸。这些两亲分子在室温下的芳香烃、环已烷和氯代烃等有机溶剂中能够形成热可逆凝胶。研究了酰胺官能团、烃尾链长度以及两亲分子头基的手性对在有机溶剂中促进凝胶形成的能力的影响。十四烷衍生物表现出最好的凝胶形成能力，而以 DL-丙氨酸为头基的两亲分子形成弱有机凝胶。酰胺基团被酯基取代的 4-十二烷氧基苯甲酸 1-羧乙基酯衍生物在稍低的温度（293 K）下也形成了弱有机凝胶。在不同溶剂中凝胶剂的凝胶数和凝胶熔化温度被确定。流变学测量表明，十四烷衍生物的有机凝胶比含有十二烷链的两亲分子的有机凝胶更强。此外，除了含有酯基的两亲分子之外，所有的有机凝胶都具有高于室温（约 303 K）的凝胶-溶胶转变温度 T(gs)，并且随着凝胶剂链长和总浓度的增加而增加。凝胶的 SEM 图像显示出纤维状结构。小角 XRD 和光学显微镜也被用来表征凝胶。除了 4-十二烷氧基苯甲酸 1-羧乙基酯的衍生物之外，丙氨酸衍生物的有机凝胶都表现出光学双折射。使用（1）H NMR 和 FTIR 光谱研究了凝胶化的机理。发现 -CO(2)H 基团之间的氢键以及 pi-pi 相互作用对凝胶化过程很重要。
