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

吸附聚合物的表面活性剂迁移及其对共吸附滞后严重程度的影响

• 批准号: 0625135
• 负责人: Robert Tilton
• 金额: $ 10万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2008-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0625135&HistoricalAwards=false
• 关键词: Surfactant; Mobilization; Adsorbed; Polymer; its

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.

项目摘要蒂尔顿河，沃什伯恩，N； 卡内基梅隆大学； CTS-0625135智力价值。有两个观察结果促进了这项研究：i）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敏感；ii）当聚合物在与聚合物结合但被固体表面排斥的表面活性剂存在下进行吸附时，滞后迹象有时会增加，但有时会减少。主要目标是确定表面活性剂结合控制吸附聚合物动力学的机制，从而确定它们对不同构象进行采样的能力及其对滞后共吸附的敏感性。聚合物/表面活性剂共吸附研究的最新技术是，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来检验滞后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该现象。该项目将提供发展适当理论所需的系统设计的实验基准。虽然该提案的重点主要在于实验研究，但将开发动力学蒙特卡罗模拟并与数据趋势进行比较。动力学 MC 模拟的重点是通过记录吸附层对溶液成分阶跃变化的响应动态来模拟实验磁滞测量。该研究的假设是，结合的表面活性剂溶解并动员聚合物“列车”链段，从而减少滞后现象。为了进入并调动列车区段，表面活性剂必须克服固体表面的排斥能垒。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以下测量：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)表面活性剂对吸附的聚合物和从本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具有强大的控制作用。它们存在于药物、陶瓷、油漆、油墨和其他高级涂料等材料的制造和应用中。聚合物/表面活性剂混合物施加强烈的耦合力来微调材料性能，但不幸的结果是这些材料特别难以配制。滞后效应的普遍存在加剧了配制困难，其中最终材料性能对组分添加顺序和混合条件敏感。通过确定滞后共吸附的起源，该项目将实现新的复杂流体配方方法，从而改进各行业的产品和工艺。该项目包括大学、工业和 K-12 教育活动。 PI 将为新的高级胶体和表面表征大学课程开发“表面活性剂吸附的椭圆光度测量”实验室模块。关于椭圆光度术的理论、实践和解释的简明讲座将与实验室模块一起提供，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。该团队将与卡内基梅隆大学的“工程你的未来”计划合作， 将女高中生带到校园进行一天的实践活动，展示日常生活中的工程。