Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering.
Droplet polydispersity and shape fluctuations in AOT [bis(2-ethylhexyl)sulfosuccinate sodium salt] microemulsions studied by contrast variation small-angle neutron scattering.
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通过对比变化小角中子散射研究 AOT [双（2-乙基己基）磺基琥珀酸钠盐]微乳液中的液滴多分散性和形状波动。
DOI：
10.1103/physreve.63.061406
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. S. Pedersen
中科院分区：
文献类型：
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作者：
L. Arleth;J. S. Pedersen
本文研究了由AOT水和正癸烷或异辛烷组成的微乳液，在相图中表面活性剂覆盖的水滴形成区域。微乳液液滴的多分散性和形状波动的测定和比较在两种不同的烷烃类型。电导率的测量表明，有一个显着的依赖性的温度行为的微乳液上使用的烷烃的类型。在这两种情况下，当温度升高时，微乳液液滴开始形成更大的聚集体。但在含有癸烷的系统中，这种聚集温度比含有异辛烷的类似系统中的温度低约10摄氏度。当AOT/D（2）O/癸烷微乳液的温度为10 ℃和AOT/D（2）O/异辛烷微乳液的温度为20 ℃时，避免了聚集现象，并且两个体系相对于聚集温度处于大致相同的降低温度。对比度变化小角中子散射测量进行在这些温度下的系统与体积分数为5%D2O +AOT通过改变烷烃的散射长度密度。对于每个样本，研究了均匀分布在匹配点周围的11种不同对比度的小角散射。不同的对比度的散射数据进行了分析，使用分子约束模型覆盖的AOT，相互作用的多分散硬球的椭圆形水滴。通过考虑不同的对比度因子，同时拟合所有对比度。分析表明，在相对于聚集温度相同的还原温度下，两种体系中的液滴尺寸、多分散指数、形状波动的大小相似。AOT/D（2）O/癸烷微乳液的多分散指数（σ/R）为16%，液滴的平均轴比为1.56。AOT/D（2）O/异辛烷体系的多分散指数也为16%，轴比为1.72。弯曲弹性常数kappa和高斯弯曲弹性常数kappa可以从这些数字估计。对于AOT/D（2）O/癸烷，我们得到kappa=3.4 k（B）T和kappa=-5.9 k（B）T;对于AOT/D（2）O/异辛烷，我们得到kappa= 2.35 k（B）T和kappa=-3.8 k（B）T，其中k（B）是Boltzmann常数，T是绝对温度。
Microemulsions consisting of AOT water, and decane or iso-octane are studied in the region of the phase diagram where surfactant covered water droplets are formed. The polydispersity and shape fluctuations of the microemulsion droplets are determined and compared in the two different alkane types. Conductivity measurements show that there is a pronounced dependence of the temperature behavior of the microemulsion on the type of alkane used. In both cases the microemulsion droplets start to form larger aggregates when the temperature increases. But in the system with decane this aggregation temperature occurs at a temperature about 10 degrees C lower than in a similar system with iso-octane. Aggregation phenomena are avoided and the two systems are at approximately the same reduced temperature with respect to the aggregation temperature when the temperature of the AOT/D(2)O/decane microemulsion is 10 degrees C and the temperature of the AOT/D(2)O/iso-octane microemulsion is 20 degrees C. Contrast variation small-angle neutron scattering measurements are performed at these temperatures on systems with volume fractions of 5% D2O+AOT by varying the scattering length density of the alkane. The small-angle scattering for 11 different contrasts evenly distributed around the match points are studied for each sample. The scattering data for the different contrasts are analyzed using a molecular constrained model for ellipsoidal droplets of water covered by AOT, interacting as polydisperse hard spheres. All contrasts are fitted simultaneously by taking the different contrast factors into account. The analysis show that at the same reduced temperature with respect to the aggregation temperature the droplet size, polydispersity index, the size of the shape fluctuations are similar in the two systems. A polydispersity index (sigma/R of the Gaussian size distribution) of 16% and an average axis ratio of the droplets of 1.56 is found in the AOT/D(2)O/decane microemulsion. In the AOT/D(2)O/iso-octane system the polydispersity index is also 16% while the axis ratio is 1.72. The bending elastic constant kappa and the Gaussian bending elastic constant kappa; can be estimated from these numbers. For AOT/D(2)O/decane we find kappa=3.4 k(B)T and kappa=-5.9 k(B)T and for AOT/D(2)O/iso-octane we find kappa=2.35k(B)T and kappa=-3.8k(B)T, where k(B) is the Boltzmann constant and T is the absolute temperature.