Synthesis, Structure and Swelling of Polyelectrolyte Brushes

建议编号：CBET-0730696首席研究员：S.Michael KilNorth大学/机构：克莱姆森大学标题：聚电解质刷子的合成、结构和溶胀本实验项目的目标是梳理出明确定义的聚电解质(PE)体系的电荷和链构象之间的相互缠绕的联系。这将通过研究“弱”和“强”PE刷子的分子级结构作为大小和拴系密度的函数，以及设置体系pH值和一价盐浓度的电荷状态的参数来实现。由于纳米结构决定了界面上相互作用的范围和强度，因此了解PE刷子如何根据溶液环境的变化调整其分子水平的溶剂化结构(垂直于或横向于系绳表面)对于创建具有定制性能的PE改性表面是必要的。这项研究的结果将影响PE的许多应用，包括粘合剂、防污或类似润滑的涂层、药物输送系统和生物材料表面。这项研究得益于开发了一种可靠的方法，可以直接合成定义明确的聚甲基丙烯酸(PMAA)和聚苯乙烯磺酸钠(PSS)PE刷子，并且可以使用橡树岭国家实验室(ORNL)的世界级中子科学设施。这些弱(PMAA)和强(PSS)PE刷子的分子级结构将使用镜面和非镜面中子反射率测量来研究，并辅之以原子力显微镜拓扑成像和平均层厚度的多角度椭偏测量。通过与ORNL散裂中子源的John Ankner博士和田纳西大学和ORNL.的Jimmy Mays教授的合作，这项研究工作得到了加强。系统地研究表面密度、大小、pH、盐的类型和浓度对强、弱PE刷的分子级结构和溶胀行为的影响，将为理解PE刷体系中构象和电荷之间的复杂联系提供一个框架。基于原子转移自由基聚合的新的合成策略克服了制造PE刷子的其他方法的局限性。除了提供弱PE刷子和强PE刷子如何调整其垂直于表面和沿表面的结构的纳米级视图外，结果还将用于从理论上仲裁预测。这项拟议的工作通过检查离子特定效应，包括与节肢动物事件的关键生物分子的相互作用，以及PE刷子中的内部盐分浓度如何依赖于系留密度和pH，开辟了新的领域。与ORNL科学家的合作建立在既定的记录基础上，将有助于确保成功的结果。拟议活动的广泛影响。了解PE刷子的结构对于广泛的应用非常重要，包括粘合剂或防污涂层、胶体稳定化以及生物材料涂层或药物输送载体、传感器和电流变开关的开发。这项研究的结果可能会激发人们对如何设计具有定制性能的生物材料或膜涂层、传感器或微流控设备的致动器层或高亲和力分离剂的新想法。该项目将加强克莱姆森大学和ORNL之间的互动，并通过合作，促进研究生和本科生的专业和个人成长。作为散裂中子源的第一批用户之一，研究人员将与ORNL合作，向更广泛的受众介绍他们的研究和中子科学在材料界面研究中的意义。除了为来自代表性不足群体的年轻工程师的发展提供培训基础外，还将发起一项新的努力，旨在为有抱负的中等科学教育专业的学生提供真实的、基于发现的研究体验。这一努力旨在帮助即将成为教师的教师更好地掌握将发现和科学探究经验融入课堂的能力，从而激发未来几代学生的兴趣。

Proposal Number: CBET- 0730696Principal Investigator: S. Michael KilbeyUniversity/Institution: Clemson University Title: Synthesis, Structure and Swelling of Polyelectrolyte Brushes The goal of this experimental project is to tease apart the intertwined connections between charge and chain conformation of well-defined polyelectrolyte (PE) systems. This will be accomplished by investigating the molecular-level structure of "weak" and "strong" PE brushes as a function of size and tethering density, and parameters that set the charge state of the system pH and monovalent salt concentration. As the nanoscale structure dictates the range and strength of interactions across interfaces, knowledge of how PE brushes adjust their molecular-level, solvated structure, both normal to and laterally along the tethering surface, in response to changes in their solution environment is necessary for the creating PE-modified surfaces with tailored properties. Results from the research will impact many applications for PEs, including adhesive, anti-fouling, or lubrication-like coatings, drug-delivery systems, and biomaterial surfaces. This research is enabled by the development of a robust method to directly synthesize well-defined PE brushes of poly(methacrylic acid) (PMAA) and sodium-poly(styrene sulfonate) (PSS) and access to world-class facilities for neutron science at Oak Ridge National Laboratory (ORNL). The molecular-level structure of these weak (PMAA) and strong (PSS) PE brushes will be studied using specular and off-specular neutron reflectivity measurements, complemented by atomic force microscopy imaging of the topology and multi-angle ellipsometry measurements of the average layer thickness. The research effort is enhanced by collaboration with Dr. John Ankner of the Spallation Neutron Source at ORNL, and Prof. Jimmy Mays of the University of Tennessee and ORNL.Intellectual Merits of the Proposed Activity. The proposed systematic study of the effect of surface density, size, pH, and salt type and concentration on the molecular-level structure and swelling behavior of strong and weak PE brushes will provide a framework for understanding the complex connections between conformation and charge in PE brush systems. The novel synthetic strategy based on atom-transfer radical polymerization overcomes limitations associated with alternative approaches for making PE brushes. In addition to providing a nanoscale view of how weak and strong PE brushes adjust their structure normal to and along the surface, results will be used to arbitrate predictions from theory. The proposed work breaks new ground by examining ion specific effects, including interactions with a biomolecule key to thromobotic events, and how the internal salt concentration in PE brushes depends upon tethering density and pH. The collaborations with ORNL scientists, which build on an established track record, will help ensure successfuloutcomes.Broader Impacts of the Proposed Activity. Understanding the structure of PE brushes is important for a wide range of applications, including adhesive or anti-fouling coatings, colloid stabilization, and the development of biomaterial coatings or drug delivery vehicles, sensors and electrorheological switches. Results from the research may stimulate new ideas about how to engineer biomaterial or membrane coatings with tailored properties, actuating layers for sensors or microfluidic devices, or high-affinity separation agents. This project will enhance interactions between Clemson University and ORNL and through the collaborations, foster the professional and personal growth of graduate and undergraduate students. As a result of being some of the first users of the Spallation Neutron Source, researchers will work with ORNL to contextualize and communicate to broader audiences the significance of their research and neutron science in the study of material interfaces. In addition to providing a training ground for the development of young engineers from underrepresented groups, a new effort aimed at providing an authentic, discovery-based research experience for aspiring secondary science education majors will be launched. This effort is aimed at helping soon to be teachers become better equipped to incorporate discovery and scientific inquiry experiences into their classrooms, thereby fueling the interests of future generations of students.