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水溶液中β-环糊精与双子表面活性剂之间的包合物:一项核磁共振研究。

Inclusion complexes between beta-cyclodextrin and a Gemini surfactant in aqueous solution: an NMR study.

作者信息

Guerrero-Martínez Andrés, González-Gaitano Gustavo, Viñas Montserrat H, Tardajos Gloria

机构信息

Departamento de Química-Física I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain.

出版信息

J Phys Chem B. 2006 Jul 20;110(28):13819-28. doi: 10.1021/jp0615813.

Abstract

(1)H NMR spectra, diffusion-ordered NMR (DOSY), and 2D rotating-frame Overhauser enhancement spectroscopy (ROESY) experiments for aqueous solutions at 298 K containing the gemini surfactant, bis (dodecyl dimethylammonium)diethyl ether dibromide (12-EO(1)-12), in the absence and presence of beta-cyclodextrin (beta-CD) were used to characterize the surfactant and to determine the effects of the complexation in the micellization. For the binary system, the critical micelle concentration (cmc), the aggregation number, the stepwise micellization constant, and the size of the monomer have been obtained by studying the dependence of the chemical shifts and the self-diffusion coefficients with the concentration of surfactant. For the ternary system, the analysis of the (1)H NMR spectra and the self-diffusion coefficients reveal the formation of complexes of 1:1 and 2:1 stoichiometry (beta-CD:gemini), with a calculated stability constant for the second binding step higher than that of the first. The values of the hydrodynamic radii of the complexes were obtained from the calculated diffusion coefficients. The presence of beta-CD modifies the cmc in an extension that indicates mainly the formation of a 2:1 complex. The analysis of the chemical shifts of the surfactant indicates the nonparticipation of the complexes into the micelles. ROE enhancements depend substantially on the amount of the macrocycle added and therefore on the stoichiometry; at low concentrations of beta-CD, one of the hydrocarbon chains binds favorably with the cavity whereas the other interacts with the outer face. By contrast, at higher concentrations of beta-CD, the two hydrocarbon tails are included in two different macrocycles.

摘要

对298K下含有双子表面活性剂双(十二烷基二甲基铵)二乙醚二溴化物(12-EO(1)-12)的水溶液,在不存在和存在β-环糊精(β-CD)的情况下进行了¹H NMR光谱、扩散排序NMR(DOSY)和二维旋转框架Overhauser增强光谱(ROESY)实验,以表征表面活性剂并确定络合作用对胶束形成的影响。对于二元体系,通过研究化学位移和自扩散系数与表面活性剂浓度的关系,获得了临界胶束浓度(cmc)、聚集数、逐步胶束化常数和单体尺寸。对于三元体系,¹H NMR光谱和自扩散系数的分析揭示了化学计量比为1:1和2:1(β-CD:双子表面活性剂)的络合物的形成,计算得出的第二步结合的稳定性常数高于第一步。从计算出的扩散系数获得了络合物的流体动力学半径值。β-CD的存在使cmc发生了变化,这主要表明形成了2:1的络合物。表面活性剂化学位移的分析表明络合物不参与胶束的形成。ROE增强主要取决于大环化合物的添加量,因此取决于化学计量比;在低浓度的β-CD下,其中一条烃链与空腔有利地结合,而另一条与外表面相互作用。相比之下,在较高浓度的β-CD下,两条烃链被包含在两个不同的大环中。

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