Interaction of Water with Polymer Surfaces: Consequence on Wetting, Adhesion, and Friction

水与聚合物表面的相互作用：对润湿、粘附和摩擦的影响

• 批准号: 1610483
• 负责人: Ali Dhinojwala
• 金额: $ 40.5万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2022-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1610483&HistoricalAwards=false
• 关键词: Interaction; Water; Polymer; Surfaces; Consequence

NON-TECHNICAL SUMMARY:The interaction of water with polymer surfaces has significant implications in diverse technological areas. The impacts are far-reaching: from energy-harvesting devices, biomedical implants, corrosion-resistant coatings, and extending to any innovation with surfaces that is influenced by wettability in aqueous environments. The goal of this project is to understand how polymer surfaces restructure themselves on a molecular level after coming in contact with water. Polymers are widely used as adhesives and lubricants and the knowledge of how these materials interact with water is of great importance. This understanding will be obtained using advanced specialized surface and spectroscopic techniques, some developed in the PI's laboratory. The fundamental understanding developed by the planned research will help in designing better materials that either adapt or resist changes upon contact with water. The PI will be training two graduate students in the area of surface science, which is a key requirement of industries developing or manufacturing adhesives or coatings. In addition to these directly integrated educational aspects, the PI will also be involved in broader outreach activities to middle and high school students as well as to community colleges. TECHNICAL SUMMARY:It is well accepted that when we bring water in contact with surfaces, polar groups can migrate or reorient at the contact interface and reduce the interfacial energy. This surface rearrangement results in contact angle hysteresis. For example, when two solid surfaces come in contact, this interfacial rearrangement leads to adhesion hysteresis and higher friction. But the direct observations of these structural rearrangements are elusive. Surface-sensitive sum frequency generation spectroscopy (SFG) has been used to study surface rearrangements upon contact with water, changes during solid-solid contact, and during sliding contact. However, the kinetics of the surface rearrangements in contact with water are not well understood, particularly how dynamical effects are related to the Tg of the polymer or even surface Tg. The PI will conduct SFG experiments to study the kinetics of surface rearrangements for poly(alkyl methacrylates) and poly(alpha-hydroxymethyl substituted acrylate) as a function of time and temperature after bringing the surfaces in contact with water, humidity, and steam. This will allow the PI to relate these surface changes with contact-angle hysteresis and adhesion hysteresis underwater, and to study the differences between wet and dry friction coefficients. Recently, the PI and his collaborators have shown that molecular dynamics (MD) simulations are able to reproduce the SFG spectra of the poly(methyl methacrylate) surface. Here, the PI will complement the SFG experiments with MD simulations for polymer-water interfaces. The proposed research will be a concerted effort at the molecular-level to understand the interaction of water with polymer surfaces.

非技术总结：水与聚合物表面的相互作用在不同的技术领域具有重要意义。影响是深远的：从能量收集设备、生物医学植入物、耐腐蚀涂层，并扩展到任何具有受水性环境中润湿性影响的表面的创新。 该项目的目标是了解聚合物表面在与水接触后如何在分子水平上进行重组。聚合物被广泛用作粘合剂和润滑剂，了解这些材料如何与水相互作用非常重要。这种理解将通过使用先进的专业表面和光谱技术来获得，其中一些是在PI的实验室开发的。 计划中的研究开发的基本理解将有助于设计更好的材料，无论是适应或抵抗与水接触后的变化。PI将培养两名表面科学领域的研究生，这是开发或制造粘合剂或涂料行业的关键要求。除了这些直接整合的教育方面，PI还将参与更广泛的外展活动，以初中和高中学生以及社区学院。技术总结：人们普遍认为，当我们使水与表面接触时，极性基团可以在接触界面处迁移或重新取向，并降低界面能。这种表面重排导致接触角滞后。例如，当两个固体表面接触时，这种界面重排导致粘附滞后和更高的摩擦。但是这些结构重组的直接观察是难以捉摸的。表面敏感和频发生光谱（SFG）已被用来研究表面重排后，与水接触，在固体-固体接触过程中的变化，并在滑动接触。然而，与水接触的表面重排的动力学还没有很好地理解，特别是动力学效应如何与聚合物的Tg或甚至表面Tg相关。 PI将进行SFG实验，以研究聚（甲基丙烯酸烷基酯）和聚（α-羟甲基取代丙烯酸酯）在表面与水、湿度和蒸汽接触后，表面重排动力学随时间和温度的变化。这将允许PI将这些表面变化与接触角滞后和水下附着滞后联系起来，并研究湿摩擦系数和干摩擦系数之间的差异。最近，PI和他的合作者已经表明，分子动力学（MD）模拟能够再现聚（甲基丙烯酸甲酯）表面的SFG光谱。在这里，PI将补充SFG实验与MD模拟聚合物-水界面。拟议的研究将是在分子水平上的协同努力，以了解水与聚合物表面的相互作用。