Materials World Network: Polyelectrolyte Brushes: Understanding Multi-Valent Effects on Structure and Properties

材料世界网络：聚电解质刷：了解多价对结构和性能的影响

• 批准号: 0710521
• 负责人: Matthew Tirrell
• 金额: $ 45.6万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0710521&HistoricalAwards=false
• 关键词: Materials; World; Network; Polyelectrolyte; Brushes

This comprehensive program between the University of California at Santa Barbara and the Universitt Bayreuth in Germany aims at deepening understanding and uncovering new phenomena in systems of polyelectrolyte brushes immersed in multi-valent ionic media containing metal ions, charged surfactants, molecular ions, proteins and oppositely charged polyelectrolytes. Recent preliminary work via surface force measurement has shown new behavior, relative to that in mono-valent salt, of polyelectrolyte brushes in multi-valent media. The Surface Forces Apparatus has been used to demonstrate the extended configurations and long-range forces exerted by and between brushes immersed in good solvents. In particular, there are strong collapse transitions in some multi-valent media, observable of both flat and highly curved surfaces. New behavior signals new properties in a range of important applications of polyelectrolyte brushes. Polyelectrolyte surface properties in multi-valent ionic media, such as in physiological environments, surfaces of medical devices, rheology of water-based suspensions, flocculation or condensation of polyelectrolytes, or in the hard household water and surfactant mixtures in which many personal care products are employed, may not be straightforwardly inferred from experiments in mono-valent salt, which constitute our current knowledge base. Soft interfaces that consist of charged macromolecules, highly swollen with water, are the norm in biology, such as the cellular glycocalyx, the surfaces of lung tissue, eyelids and articular cartilage, and the interfaces between mineralized collagen fibrils in bone. Commercial products, such as those for personal care (e.g., shampoo, skin care), medical prostheses (e.g., joint replacements), materials processing (e.g., sterically stabilized dispersions of suspended particles or assemblies), anti-fogging surfaces, and gene chips, also often rely on highly hydrated, charged polymer interfaces.The results of this work are anticipated to have applications in biology and medicine, water purification, water-based pigments, paints and coatings and the cosmetic product industry. By virtue of the collaboration between UC Santa Barbara (UCSB) and the Universitt Bayreuth (UB) that this proposed work will enable, a clear picture will emerge of how experiments on polyelectrolytes tethered to flat surfaces (at UCSB) connect with highly curved brushes (at UB), common to the surfaces of dispersed colloids. The same physics of polymers and ion confinement is at play in both systems. Many of the practical situations cited above can involve multi-valent ions for which there is much less experimental information and fewer established theoretical principles, than for media comprising mono-valent ions exclusively. Biological buffers, for example, typically contain many ionic species, including multi-valents. Multi-valent interactions, known to have strong effects on polyelectrolytes in solution, as in the condensation of DNA, have been studied very little in their effects on interfacially tethered polyelectrolytes, despite many studies in free solution and the broad biological and technological significance charged interfaces. Polymer chains in tethered assemblies (surface brushes, chains tethered to particles, and highly branched macromolecules) provide an experimental "grip" on the tethered ends of the macromolecules, which enables direct measurement of forces in a way that cannot be done with free linear polymers in solution.

圣巴巴拉的加州大学和德国的拜罗伊特大学之间的这一综合项目旨在加深对浸在含有金属离子、带电表面活性剂、分子离子、蛋白质和带相反电荷的聚电解质的多价离子介质中的电刷系统的理解和揭示新现象。最近的初步工作，通过表面力的测量显示了新的行为，相对于在一价盐中，在多价介质中的刷。表面力装置已被用来证明的扩展配置和长程力施加的刷子和之间浸入良好的溶剂。特别是，在一些多价介质中，可以观察到平坦和高度弯曲的表面都有强烈的塌陷过渡。新的行为标志着在一系列重要的应用程序的笔刷新的属性。聚电解质在多价离子介质中的表面性质，例如在生理环境中、医疗器械的表面、水基悬浮液的流变学、聚电解质的絮凝或凝聚，或在使用许多个人护理产品的硬家用水和表面活性剂混合物中，可能不能从构成我们当前知识基础的单价盐的实验中直接推断。由带电大分子组成的柔软界面，用水高度溶胀，是生物学中的标准，例如细胞糖萼，肺组织，眼睑和关节软骨的表面，以及骨中矿化胶原纤维之间的界面。商业产品，例如用于个人护理的产品（例如，洗发水，皮肤护理），医用假体（例如，关节置换），材料处理（例如，空间稳定的悬浮颗粒分散体或组装体）、防雾表面和基因芯片也常常依赖于高度水合的带电聚合物界面。这项工作的结果预计将在生物学和医学、水净化、水基颜料、油漆和涂料以及化妆品工业中得到应用。由于加州大学圣巴巴拉分校（UCSB）和拜罗伊特大学（UB）之间的合作，这项拟议的工作将使，一个清晰的图片将出现如何实验的聚电解质拴在平坦的表面（在UCSB）连接高度弯曲的刷子（在UB），常见的分散胶体的表面。聚合物和离子约束的相同物理在两个系统中起作用。上面引用的许多实际情况可能涉及多价离子，与仅包含单价离子的介质相比，多价离子的实验信息和建立的理论原理要少得多。例如，生物缓冲液通常含有许多离子物质，包括多价离子。多价相互作用，已知在溶液中的聚电解质有很强的影响，如在DNA的缩合，已经研究了很少在其影响上的界面束缚聚电解质，尽管许多研究在自由溶液和广泛的生物和技术意义的带电界面。拴系组件中的聚合物链（表面刷、拴系到颗粒的链和高度支化的大分子）在大分子的拴系末端上提供实验性“抓持”，这使得能够以溶液中的游离线性聚合物不能完成的方式直接测量力。