NMR Study of Surfactant Micelle Shape Transformation with Concentration
NMR Study of Surfactant Micelle Shape Transformation with Concentration
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DOI：
10.3866/pku.whxb20090714
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发表时间：
2009-07
期刊：
影响因子：
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通讯作者：
Lu Xing-Yu;Jiang Yan;Cui Xiao-hong;Mao Shi-zhen;Liu Maili;Du You-Ru
中科院分区：
文献类型：
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作者：
Lu Xing-Yu;Jiang Yan;Cui Xiao-hong;Mao Shi-zhen;Liu Maili;Du You-Ru
采用H-1核磁共振（NMR）技术研究了叔辛基苯基苯酚聚乙二醇醚（TX-100）、十二烷基苯磺酸钠（SDBS）和十四烷基三甲基溴化铵（TTAB）在重水溶液中的胶束形态转变，并进行了核磁共振自扩散实验。实验结果表明，在远高于临界胶束浓度（cmc）的浓度下，表面活性剂形成了多种形状的胶束（球形、椭球形和棒状）。在常温、常压和表面活性剂浓度大于cmc时，无其他添加剂，形成球形胶束。在较高的表面活性剂浓度下，H-1核磁共振谱和自扩散实验表明，它们的化学位移（δ）和自扩散系数(D)发生了突变。这表明球形胶束转变为更大的胶束。通过仔细检查H-1核磁共振谱中的每个质子共振峰，我们发现靠近头基团的质子比靠近疏水基团的质子经历了更大的化学位移变化。这表明表面活性剂胶束的形状很可能从球形转变为椭球状或棒状。
The micelle shape transformation of tert-octylpheny phenol polyethylene glycol ether (TX-100), sodium dodecyl benzene sulfonate (SDBS) and tetradecyl trimethyl ammonium bromide (TTAB) in heavy water solutions was studied by H-1 nuclear magnetic resonance (NMR) spectroscopy, including an NMR self-diffusion experiment. These experiments showed that the surfactants formed several shapes of micelles (spherical, ellipsoidal, and rodlike) at the respective concentrations which were far above their critical micelle concentration (cmc). At ambient temperature, normal pressure and when the concentration of the surfactant was above the cmc without other additives, spherical micelles were formed. At higher surfactant concentrations, H-1 NMR spectra and self-diffusion experiments showed that abrupt changes occurred in their chemical shifts (delta) and in their self-diffusion coefficients (D). This indicated that spherical micelles transformed into larger micelles. By careful examination of every proton resonance peak in the H-1 NMR spectra, we found that the protons near the head group experienced larger chemical shift changes than protons near the hydrophobic group. This suggests that the shape of surfactant micelles most likely transforms from spherical to ellipsoidal or rodlike.