Danov Krassimir D, Kralchevsky Peter A, Stoyanov Simeon D, Cook Joanne L, Stott Ian P
Department of Chemical and Pharmaceutical Engineering, Faculty of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria.
Department of Chemical and Pharmaceutical Engineering, Faculty of Chemistry and Pharmacy, Sofia University, Sofia 1164, Bulgaria.
J Colloid Interface Sci. 2019 Jul 1;547:245-255. doi: 10.1016/j.jcis.2019.03.105. Epub 2019 Apr 1.
A quantitative molecular-thermodynamic theory of the growth of giant wormlike micelles of nonionic surfactants can be developed on the basis of a generalized model, which includes the classical "phase separation" and "mass action" models as special cases. The generalized model describes spherocylindrical micelles, which are simultaneously multicomponent and polydisperse in size.
By analytical minimization of the free-energy functional we derived explicit expressions for the chain-extension and chain-end distribution functions in the hydrocarbon core of mixed micelles from two surfactants of different chainlengths.
The hydrocarbon core of a two-component micelle is divided in two regions, outer and inner, where the ends of the shorter and longer chains are located. The derived analytical expression for the chain-conformation free energy implies that the mixing of surfactants with different chainlengths is always nonideal and synergistic, i.e. it leads to decrease of the micellar free energy and to enhancement of micellization and micelle growth. The derived expressions are applicable to surfactants with different headgroups (nonionic, ionic, zwitterionic) and to micelles of different shapes (spherical, wormlike, lamellar). The results can be incorporated in a quantitative theory of the growth of giant mixed micelles in formulations with practical applications in detergency.
基于一个广义模型，可以建立非离子表面活性剂巨型蠕虫状胶束生长的定量分子热力学理论，该广义模型将经典的“相分离”和“质量作用”模型作为特殊情况包含在内。广义模型描述了球形柱状胶束，其在尺寸上同时具有多组分和多分散性。
通过对自由能泛函进行解析最小化，我们从两种不同链长的表面活性剂混合胶束的烃核中推导出了链延伸和链端分布函数的显式表达式。
双组分胶束的烃核分为外部和内部两个区域，较短和较长链的末端分别位于这两个区域。推导得到的链构象自由能的解析表达式表明，不同链长表面活性剂的混合总是非理想且具有协同作用的，即这会导致胶束自由能降低，并增强胶束化和胶束生长。推导得到的表达式适用于具有不同头基（非离子、离子、两性离子）的表面活性剂以及不同形状（球形、蠕虫状、层状）的胶束。这些结果可纳入巨型混合胶束生长的定量理论中，用于具有实际洗涤应用的配方中。
