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Deposition, Equilibrium Structure and Mechanical Response of Polyelectrolyte Complexes

聚电解质复合物的沉积、平衡结构和机械响应

基本信息

批准号：
1710491
负责人：
Kenneth Shull
金额：
$ 41.32万
依托单位：
Northwestern University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-09-01 至 2020-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1710491&HistoricalAwards=false
关键词：
Deposition Equilibrium Structure Mechanical Response

项目摘要

NON-TECHNICAL SUMMARY:Polyelectrolytes are large water-soluble molecules that contain electric charges. When water solutions of positively and negatively charged polyelectrolytes are mixed together, complexes are often formed that have either liquid-like or solid-like properties. The ability to tailor these properties has led to their use in a variety of applications, ranging from personal care to industrial waste processing and water treatment. This project is aimed at understanding how the relevant properties of these materials originate from the detailed structure of the components from which they are formed. This understanding will be generated by developing a series of well-characterized model materials systems, and studying their mechanical properties with several experimental techniques. In addition, new processing methods will be developed that enable polyelectrolyte complexes to easily be coated onto different material surfaces. The characterization methods include the use of high frequency sound waves to probe the material response. This technique is widely applicable to a variety of coatings with both protective and aesthetic functions. The project is relevant to membranes for water filtration and includes education and research training of students, broadening participation, and outreach activities.TECHNICAL SUMMARY:Polyelectrolyte complexes formed by the interaction of oppositely charged macromolecules are an important class of soft, polymeric materials. These materials are of interest largely because of their mechanical and transport properties. The mechanical properties can span the full spectrum of behaviors from low-viscosity liquids to tough viscoelastic materials to brittle solids, in a manner that can be reversibly controlled through changes in the salt concentration or pH. The primary aim of this project is to understand the factors that control this behavior using well-characterized model systems. A secondary aim is to use this information to develop surface modifications to enhance the performance of membranes used for water purification. The focus of the project is on polyelectrolyte complexes in thin film form, both because of the utility of these materials as surface modifiers, and because the thin film geometry is particularly convenient for the proposed investigations. There are three aspects of these investigations, beginning with new deposition mechanisms based on the electrochemical control of the pH at the surface of interest. The second set of experiments is aimed at mapping out the phase behavior of these materials, including the relationship between equilibrium water content of a film and the salt concentration of the aqueous medium with which it is in contact. The third element of the proposed program is the most extensive, and involves mechanical characterization of the polyelectrolyte complex films. Acoustic methods will be used to characterize the linear viscoelastic properties of these materials on a time-scale of about 60 nanoseconds, approaching the timescale that is accessible by molecular dynamics simulations, bridging the gap between experiment and computational modeling. In addition, the nonlinear properties of these materials will be investigated using creep and fracture experiments designed specifically for investigations of thin films in the hydrated state.

非技术综述：聚电解质是含有电荷的大的水溶性分子。当带正电和带负电的聚电解质的水溶液混合在一起时，通常会形成具有类液体或类固体性质的络合物。定制这些特性的能力导致它们在各种应用中使用，从个人护理到工业废物处理和水处理。这个项目的目的是了解这些材料的相关性能是如何从组成它们的组件的详细结构中产生的。这种理解将通过开发一系列具有良好特性的模型材料系统，并用几种实验技术研究它们的机械性能来产生。此外，还将开发新的加工方法，使聚电解质复合体能够轻松地被涂覆到不同的材料表面。表征方法包括使用高频声波来探测材料的响应。该技术广泛适用于各种兼具防护和美观功能的涂料。该项目与水过滤用膜有关，包括对学生的教育和研究培训、扩大参与和推广活动。技术摘要：由相反电荷的大分子相互作用形成的聚电解质络合物是一类重要的软聚合物材料。这些材料之所以引起人们的兴趣，很大程度上是因为它们的机械和运输性能。机械性能可以跨越从低粘度液体到坚韧的粘弹性材料再到脆性固体的所有行为范围，其方式可以通过改变盐浓度或pH进行可逆控制。这个项目的主要目标是使用特征良好的模型系统来了解控制这种行为的因素。第二个目标是利用这些信息开发表面改性，以提高用于水净化的膜的性能。该项目的重点是薄膜形式的聚电解质络合物，这既是因为这些材料作为表面改性剂的用途，也是因为薄膜的几何形状对于拟议的研究特别方便。这些研究有三个方面，首先是基于电化学控制感兴趣表面的pH的新的沉积机制。第二组实验旨在绘制出这些材料的相行为，包括薄膜的平衡水含量与其接触的水介质的盐浓度之间的关系。该计划的第三个要素是最广泛的，涉及聚电解质复合膜的机械表征。声学方法将被用来在大约60纳秒的时间尺度上表征这些材料的线性粘弹性性质，接近分子动力学模拟可以到达的时间尺度，弥合实验和计算建模之间的差距。此外，还将使用专门为研究水合状态下的薄膜而设计的蠕变和断裂实验来研究这些材料的非线性特性。