Spontaneous Formation of Nanovesicles in Mixtures of Nonionic and Dialkyl Chain Cationic Surfactants Studied by Surface Tension and SANS
Spontaneous Formation of Nanovesicles in Mixtures of Nonionic and Dialkyl Chain Cationic Surfactants Studied by Surface Tension and SANS
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DOI：
10.1021/la802435h
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发表时间：
2009-04-07
期刊：
影响因子：
3.9
通讯作者：
Cousin, F.
中科院分区：
文献类型：
--
作者：
Grillo, I.;Penfold, J.;Cousin, F.
用表面张力和小角中子散射研究了双十二烷基二甲基溴化铵（DDAB）/四甘醇单十二烷基醚（C12 E4/D2 O）三元体系稀相部分聚集体的表面性质和结构。对于表面活性剂的摩尔比，Rn，在0.3和1之间（纯DDAB），表面张力测量显示存在两个断点，浓度分别为10（-5）和10（-3）mol/L。SANS测量表明，第一个断点对应于临界胶束浓度（cmc），第二个断点对应于临界囊泡浓度（cvc）。在中间组成范围，Rn = 0.3-0.8，形成非常小的单层囊泡（纳米囊泡），其内径在28和85 A之间变化，双层厚度类似于23埃。在Rn = 0.8时，我们观察到从小囊泡（V）到大双层或多层囊泡（BLV，MLV）的过渡，其具有约1000埃的相对大的层状周期性。在非离子丰富的区域低于Rn = 0.3，观察到更经典的表面张力行为，只有一个断点对应于小球状胶束的形成的发病。
Surface tension and small-angle neutron scattering have been used to characterize the surface properties and the structure of the aggregates formed in the dilute part of the ternary system didodecyldimethyl ammonium bromide, DDAB/tetraethylene glycol monododecyl ether, C12E4/D2O. For surfactant molar ratios, Rn, between 0.3 and 1 (pure DDAB), the surface tension measurements show the existence of two break points at concentrations of around 10(-5) and 10(-3) mol/L, respectively. The SANS measurements have shown that the first break point corresponds to a critical micellar concentration (cmc) and the second one corresponds to a critical vesicle concentration (cvc). In the intermediate composition range, Rn = 0.3-0.8, very small unilamellar vesicles (nanovesicles) are formed with the inner radius varying between 28 and 85 A and a bilayer thickness of similar to 23 angstrom. At Rn = 0.8, we observed a transition from small vesicles (V) to large bilamellar or multilamellar vesicles (BLV, MLV) with a relatively large lamellar periodicity of around 1000 angstrom. In the nonionic-rich region below Rn = 0.3, more classical surface tension behavior was observed, with only one break point corresponding to the onset of formation of small globular micelles.