Structure-Kinetics Relationships in Micellar Solutions

表面活性剂在流体界面的吸附动力学对于表面活性剂在油墨、喷雾剂、润滑剂、洗涤剂、乳液和多相胶体悬浮液中的各种应用起着至关重要的作用。水中的表面活性剂通常高于临界胶束浓度；因此，胶束或其他聚集体在决定表面活性剂向界面的质量传递方面起着重要作用。先前的工作表明，胶束过程动力学的知识——胶束分解、扩散和吸附——对于胶束溶液中吸附动力学的定性理解是必不可少的。然而，我们对胶束动力学的理解还远远不够完善：胶束不吸附的标准假设并不普遍有效；在远离平衡态的胶束溶液中几乎没有动力学数据；用不同的技术测量胶束分解率可能会有数量级的差异；我们从表面活性剂的结构预测胶束过程的速率常数的能力是有限的。这一建议将发展胶束对质量输运过程的影响的定性和定量的理解。系统地改变表面活性剂的结构，并测量其对胶束结构、胶束破裂率和扩散率的影响。在1 ms - 1 s的时间尺度上，研究了液体射流和溢出圆柱体对气液界面的吸附速率，其中流体力学和吸附速率都是独立测量的。有限元模型将用于测试胶束溶液中吸附动力学的定量模型。该项目的产出将是(i)理解化学结构、胶束结构和动力学参数之间的关系，（ii）胶束溶液中吸附动力学的有效定量模型。

The kinetics of adsorption of surfactants at fluid interfaces plays a critical role in diverse applications of surfactants in inks, sprays, lubricants, detergents, emulsions and in multiphase colloidal suspensions. Surfactants in water are commonly above the critical micelle concentration; consequently, micelles or other aggregates play an important role in determining mass transport of the surfactant to an interface. Previous work has shown that a knowledge of the kinetics of micellar processes - micelle breakdown, diffusion and adsorption - is essential for even a qualitative understanding of the dynamics of adsorption in micellar solutions. Yet our understanding of micellar kinetics is far from complete: the standard assumption that micelles do not adsorb is not generally valid; there is hardly any kinetic data on micellar solutions far from equilibrium; measurements of micelle breakdown rates by different techniques may differ by orders of magnitude; our ability to predict rate constants for micellar processes from the structure of the surfactant is limited. This proposal would develop a qualitative and quantitative understanding of the effect of micelles on mass transport processes. The surfactant structure will be systematically varied and its effect on the micelle structure, micelle breakdown rates and diffusivity measured. The rate of adsorption to the air-liquid interface will be studied on the timescale of 1 ms - 1 s in a liquid jet and overflowing cylinder, in which both the hydrodynamics and adsorption rate are independently measured. Finite element modelling will be used to test quantitative models for adsorption kinetics in micellar solutions. The outputs of the project will be (i) an understanding of the relationship between chemical structure, micellar structure and kinetic parameters, (ii) a validated, quantitative model for adsorption kinetics in micellar solutions.