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.

加州大学圣塔芭芭拉分校和德国拜罗伊特大学之间的这一综合项目旨在加深对浸没在含有金属离子、带电表面活性剂、分子离子、蛋白质和相反物质的多价离子介质中的聚电解质刷系统的新现象的理解。带电聚电解质。最近通过表面力测量进行的初步工作显示了聚电解质刷在多价介质中相对于单价盐的新行为。表面力装置已用于演示浸没在良好溶剂中的刷子和刷子之间施加的扩展配置和远程力。特别是，在一些多价介质中存在强烈的塌缩转变，在平坦和高度弯曲的表面上都可以观察到。新行为标志着聚电解质刷在一系列重要应用中的新特性。多价离子介质中的聚电解质表面特性，例如在生理环境、医疗器械表面、水基悬浮液的流变学、聚电解质的絮凝或缩合，或者在许多个人护理产品中使用的硬质家用水和表面活性剂混合物中所使用的，可能无法从单价盐的实验中直接推断出来，单价盐构成了我们当前的知识基础。由带电大分子组成、遇水高度膨胀的软界面是生物学的常态，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，例如个人护理产品（例如洗发水、皮肤护理）、医疗假体（例如关节置换物）、材料加工（例如悬浮颗粒或组件的空间稳定分散体）、防雾表面和基因芯片，也经常依赖于高度水合、带电的聚合物界面。这项工作的结果预计将在生物和医学、水净化、水性颜料、油漆和涂料以及化妆品行业中得到应用。凭借加州大学圣巴巴拉分校 (UCSB) 和拜罗伊特大学 (UB) 之间的合作，这项拟议的工作将实现，我们将清楚地了解束缚在平坦表面上的聚电解质（在 UCSB）上的实验如何与高度弯曲的刷子连接（ at UB)，常见于分散胶体的表面。聚合物和离子限制的相同物理原理在这两个系统中都发挥着作用。上述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已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种类，包括多价离子。已知多价相互作用对溶液中的聚电解质（如 DNA 缩合）有强烈影响，但对其对界面束缚聚电解质的影响却很少研究，尽管对自由溶液和具有广泛生物学和技术意义的带电界面进行了许多研究。系留组件中的聚合物链（表面刷、系在颗粒上的链和高度支化的大分子）提供了对大分子系留末端的实验“抓地力”，这使得能够以自由线性聚合物无法完成的方式直接测量力在溶液中。