Deposition, Equilibrium Structure and Mechanical Response of Polyelectrolyte Complexes

非技术总结：聚电解质是含有电荷的水溶性大分子。 当带正电荷和负电荷的聚电解质的水溶液混合在一起时，通常形成具有液体状或固体状性质的复合物。 定制这些特性的能力使其在各种应用中得到应用，从个人护理到工业废物处理和水处理。 该项目旨在了解这些材料的相关特性如何源于它们形成的组件的详细结构。 这种理解将通过开发一系列表征良好的模型材料系统，并使用多种实验技术研究其力学性能来产生。 此外，还将开发新的加工方法，使纳米复合物能够容易地涂覆到不同的材料表面上。 表征方法包括使用高频声波探测材料响应。 该技术广泛适用于各种兼具防护和美观功能的涂料。 该项目与水过滤膜有关，包括对学生的教育和研究培训、扩大参与和外联活动。技术概述：由带相反电荷的大分子相互作用形成的聚电解质复合物是一类重要的软质聚合物材料。这些材料之所以令人感兴趣，主要是因为它们的机械和传输特性。机械性能可以跨越从低粘度液体到坚韧粘弹性材料到脆性固体的全范围行为，其方式可以通过盐浓度或pH值的变化进行可逆控制。该项目的主要目的是了解使用良好表征的模型系统控制这种行为的因素。第二个目的是利用这些信息来开发表面改性，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复合物，因为这些材料作为表面改性剂的效用，因为薄膜的几何形状是特别方便的拟议调查。这些研究有三个方面，首先是基于感兴趣的表面处的pH的电化学控制的新的沉积机制。第二组实验旨在绘制出这些材料的相行为，包括膜的平衡水含量和与其接触的水性介质的盐浓度之间的关系。所提出的计划的第三个要素是最广泛的，并涉及机械表征的复合膜。声学方法将用于表征这些材料的线性粘弹性的时间尺度约为60纳秒，接近分子动力学模拟，弥合实验和计算建模之间的差距的时间尺度。此外，这些材料的非线性特性将使用蠕变和断裂实验进行研究，专门用于调查薄膜在水合状态。

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.