Surfactant Mobilization of Adsorbed Polymer and its Effect on the Severity of Co-Adsorption Hysteresis

项目摘要：蒂尔顿，r，沃什伯恩，N；卡内基梅隆大学。cts - 0625135知识价值。两个观察结果激发了所提出的研究：1)聚合物通常在固/液界面处处于持续的滞后状态，因此吸附程度和聚合物构象对吸附历史很敏感；2)当聚合物在表面活性剂的存在下吸附时，滞后的迹象有时会增加，但有时会减少，这些表面活性剂与聚合物结合，但被固体表面排斥。主要目的是确定表面活性剂结合控制被吸附聚合物动力学的机制，从而确定它们对不同构象的取样能力及其对滞回共吸附的敏感性。聚合物/表面活性剂共吸附研究的最新进展是，尽管文献中包含了越来越多的实验系统的研究，但尚未进行系统设计的实验研究，以测试迟滞共吸附的起源和控制的任何假设，也没有开发出理论模型来解释这一现象。该项目将提供系统设计的实验基准，这是发展适当理论所需要的。虽然建议的重点主要是在实验研究，动力学蒙特卡罗模拟将发展和趋势比较的数据。动力学MC模拟的特别重点是通过记录吸附层对溶液组成阶跃变化的响应的动力学来模拟实验滞后测量。所提出的研究的假设是，结合的表面活性剂可溶解和调动聚合物“列”段，从而减少迟滞。为了进入和调动列车部分，表面活性剂必须克服来自固体表面的排斥能垒。以下测量将在具有系统变化的聚合物/表面活性剂结合能和表面活性剂/表面排斥能的模型系统中进行：i)通过不同吸附途径从聚合物表面活性剂混合物中吸附的程度，ii)表面活性剂对被吸附聚合物和从体溶液进入的聚合物之间交换的程度和动力学的影响，以及iii)表面活性剂对被吸附聚合物表面扩散系数的影响。更广泛的影响。该研究项目将广泛有利于工业复杂流体配方的实践。聚合物和表面活性剂的混合自组装和共吸附对复杂流体的宏观性质起着强有力的控制作用。这些都被发现在制造和应用的材料，如药品，陶瓷，油漆，油墨和其他先进的涂料。聚合物/表面活性剂混合物施加强耦合力，微调材料性能，但不幸的是，这些材料特别难以配制。普遍存在的滞后效应加剧了配方的困难，其中最终的材料性能对组分添加的顺序和混合条件很敏感。通过确定滞回共吸附的起源，该项目将实现新的复杂流体配方方法，从而改善各种行业的产品和工艺。该项目包括大学、工业和K-12教育活动。PI将为大学新开设的“高级胶体与表面表征”课程开发“表面活性剂吸附椭圆测量”实验模块。作为工业短期课程《胶体、界面和复杂流体表征的基本仪器方法》的一部分，将与实验模块一起提供关于椭圆偏振的理论、实践和解释的简明讲座。该团队将与卡内基梅隆大学的“工程你的未来”项目合作，该项目将女高中生带入校园，进行一天的实践活动，说明日常生活中的工程。

Project AbstractTilton, r., Washburn,N; Carnegie-Mellon Univ.; CTS-0625135Intellectual Merit. Two observations motivate the proposed research: i) that polymers often reside in persistent hysteretic states at the solid/liquid interface whereby the extent of adsorption and the polymer conformation are sensitive to the adsorption history and ii) that the signs of hysteresis are sometimes increased, but sometimes decreased, when polymers adsorb in the presence of surfactants that bind to the polymer but are repelled from the solid surface. The primary objective is to determine the mechanism by which surfactant binding controls the dynamics of adsorbed polymers and thus their ability to sample different conformations and their susceptibility to hysteretic co-adsorption. The state-of-the-art in polymer/surfactant co-adsorption research is that although the literature contains studies of an increasing number of experimental systems, no systematically designed experimental study has been performed that tests any hypothesis for the origin and control of hysteretic co-adsorption, and no theoretical model has been developed to explain the phenomenon. The project will provide the systematically designed experimental benchmarks that are needed for the development of appropriate theory. While the emphasis of the proposal is mainly on the experimental studies, kinetic Monte Carlo simulations will be developed and compared to trends in the data. The particular focus of the kinetic MC simulations is to mimic experimental hysteresis measurements by recording the dynamics of adsorbed layer response to a step-change in solution composition. The hypothesis underlying the proposed research is that bound surfactants solubilize and mobilize polymer "train" segments, thereby decreasing hysteresis. In order to access and mobilize train segments, surfactants must surmount the repulsive energy barrier from the solid surface. The following measurements will be made in model systems with systematically varying polymer/surfactant binding energies and surfactant/surface repulsive energies: i) extent of adsorption from polymer surfactant mixtures via different adsorption pathways, ii) surfactant influence on the extent and kinetics of exchange between adsorbed polymers and polymers entering from the bulk solution, and iii) surfactant influence on adsorbed polymer surface diffusion coefficients.Broader Impact. The research project will broadly benefit industrial complex fluid formulation practices. Mixed self-assembly and co-adsorption of polymers and surfactants exert powerful controls over the macroscopic properties of complex fluids. These are found in the manufacture and application of materials such as pharmaceuticals, ceramics, paints, inks, and other advanced coatings. Polymer /surfactant mixtures exert strongly coupled forces that fine tune material properties, but with the unfortunate consequence that these materials are particularly difficult to formulate. Formulation difficulties are exacerbated by the prevalence of hysteresis effects, where the final material properties are sensitive to the order of component addition and mixing conditions. By determining the origins of hysteretic co-adsorption, this project will enable new complex fluid formulation methods that will lead to improved products and processes over a spectrum of industries. The project includes university, industrial, and K-12 educational activities. The PI will develop a laboratory module on Ellipsometric Measurement of Surfactant Adsorption" for a new Advanced Colloid and Surface Characterization university course. A concise lecture on theory, practice, and interpretation of ellipsometry will be offered together with the lab module as part of the industrial short course Essential Instrumental Methods for Colloid, Interface, and Complex Fluid Characterization. The team will collaborate with Carnegie Mellon's Engineering Your Future program that brings female high school students onto campus for a day of hands-on activities illustrating engineering in everyday life.