Thermodynamic stability of worm-like micelle solutions.
Thermodynamic stability of worm-like micelle solutions.
复制标题
蠕虫状胶束溶液的热力学稳定性。
DOI：
10.1039/c7sm01132f
复制
发表时间：
2017
期刊：
影响因子：
3.4
通讯作者：
Hanqiu Jiang
中科院分区：
文献类型：
--
作者：
K. Vogtt;G. Beaucage;M. Weaver;Hanqiu Jiang
蠕虫状胶束（WLM）是纳米尺度的自组装体，广泛用于粘度增强、药物递送和个人护理产品中。WLM在不同离子和表面活性剂浓度下的稳定性对于这些迷人材料的应用非常重要。在这项工作中，它表明，维里方法可以用来理解和预测WLM稳定性。用小角中子散射研究了月桂醇聚醚硫酸钠和椰油酰胺丙基甜菜碱组成的混合表面活性剂体系。第二维里系数A2和盐与表面活性剂的比例Θs-s之间存在线性关系。依赖于Θs-s的项通过本体和WLM周围的离子云之间的盐离子的缔合/解离动力学来描述，得到，其中Keq是缔合/解离常数，nsurf是摩尔表面活性剂浓度，B是摩尔排除体积，M是WLM摩尔质量，Θs-s是盐-表面活性剂比率，Θ是盐-表面活性剂比率，其中相互作用仅由排除体积确定。比值B/M2与WLM轮廓长度无关。发现在良好的溶剂中的半稀释制度的指数ψ约为5/4，与聚合物标度律一致。
Worm-like micelles (WLMs) are nano-scale self-assemblies widely used for viscosity enhancement, for drug delivery, and in personal care products. The stability of WLMs under variable ionic and surfactant concentrations is important to applications of these fascinating materials. In this work it is demonstrated that a virial approach can be used to understand and predict WLM stability. A mixed surfactant system consisting of sodium laureth sulfate and cocoamidopropyl betaine was examined using small-angle neutron scattering. A linear relationship between the second virial coefficient, A2, and the salt to surfactant ratio, Θs-s, is derived and demonstrated. The Θs-s-dependent term is described via association/dissociation kinetics of salt ions between the bulk and an ion cloud surrounding the WLMs yielding, , where Keq is the association/dissociation constant, nsurf is the molar surfactant concentration, b is the molar excluded volume, M the WLM molar mass, Θs-s is the salt-surfactant ratio and Θ is the salt-surfactant ratio where the interactions are solely determined by the excluded volume. The ratio b/M2 is independent of WLM contour length. The exponent ϑ is found to be approximately 5/4 in agreement with polymer scaling laws for the semi-dilute regime in good solvents.