Collaborative Research: The Role of Sulfonated Polymer Membrane Morphology in Microscale Transport of Organic Molecules

先进的化学传感器使诸如护理点医疗检测和个人防护设备等技术能够对抗化学战剂。化学传感器的日益复杂性来自于用作传感器的材料的进步或研究具有不寻常特性的现有材料。一种这样的材料是商业聚合物，Nafion，其用于电解，矿物提取，特种化学合成，电化学传感器和燃料电池。Nafion的广泛使用是由于其独特的化学结构，它由氟和碳原子的长疏水（防水）主链和亲水（亲水）分支组成。这些双功能性在水的存在下产生高化学稳定性、高反应性和柔性。双功能性还导致分子通过材料的独特运输，特别是当制造成薄膜时。现有的理论很好地描述了小分子在Nafion膜内的传输。然而，运输较大的有机化合物，如化学战剂中发现的那些，不能在现有的理论框架内解释，特别是当考虑到Nafion的水诱导的灵活性时。该项目将使用先进的实验技术来推断作为化学战剂代表的大有机分子通过动态Nafion膜的运输。该项目将开发一个直接的机械理解的水使能运输的有机分子通过Nafion膜。初步数据表明，大的有机分子被有效地固定在干Nafion的疏水和亲水结构域之间的第三界面区域。假设该界面的来源是主链和全氟磺酸侧链之间的氟醚键。然而，苯酚和其他弱有机酸在干燥和潮湿条件下保持固定。本计画将探讨在混合溶剂系统中，本体磺化聚苯乙烯共聚物对有机大分子之输送之界面及作用。一个跨学科的团队将采用小角中子散射，X射线散射和高磁场下的核磁共振。如果成功的话，拟议的研究将解决全氟磺酸和磺化聚苯乙烯膜中明显不同的域的结构和动态性能之间的关系。具体而言，调查将确定域形态的影响，运输，固定化和有机分子的反应性。该项目将支持研究生教育，创建新的教学模块，并展示在运输，催化和聚合物膜结构优化的交叉机会的社区推广活动。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Advanced chemical sensors enable technologies such as point-of-care medical testing and personal protective equipment against chemical warfare agents. Increasing sophistication of the chemical sensors derives from advances in the materials used as the sensor or in studying existing materials with unusual properties. One such material is the commercial polymer, Nafion, which is used in electrolysis, mineral extraction, specialty chemical synthesis, electrochemical sensors, and fuel cells. The widespread use of Nafion is due to its unique chemical structure, which is comprised of a long hydrophobic (water repellent) backbone of fluorine and carbon atoms and hydrophilic (water loving) branches. These dual functionalities give rise to high chemical stability, high reactivity, and flexibility in the presence of water. The dual functionality also leads to unique transport of molecules through the material, particularly when fabricated into a thin membrane. Transport of small molecules within the Nafion membrane is well described by existing theories. However, transport of larger organic compounds, such as those found in chemical warfare agents, cannot be explained within existing theoretical frameworks, particularly when the water-induced flexibility of Nafion is considered. This project will use advanced experimental techniques to deduce transport of large organic molecules that are representative of chemical warfare agents through the dynamic Nafion membrane. This project will develop a direct mechanistic understanding of water-enabled transport of organic molecules through Nafion membranes. Preliminary data suggests large organic molecules are effectively immobilized in a tertiary interphase region between hydrophobic and hydrophilic domains in dry Nafion. The source of this interphase is hypothesized to be the fluoroether linkage between the backbone and the perfluorosulfonic acid side chains. However, phenols and other weak organic acids remain immobilized under both dry and wet conditions. This project will probe the interphase, and the role of bulk sulfonated polystyrene copolymers on transport of large organic molecules in mixed solvent systems. An interdisciplinary team will employ small angle neutron scattering, X-ray scattering, and nuclear magnetic resonance at high magnetic fields. If successful, the proposed research will resolve the relationship between the structural and dynamic properties of the distinctly different domains in perfluorosulfonic acid and sulfonated polystyrene membranes. Specifically, the investigation will determine impact of domain morphology on the transport, immobilization, and reactivity of organic molecules. The project will support graduate education, create new teaching modules, and community outreach activities that demonstrate opportunities at the intersection of transport, catalysis and structure optimization of polymeric membranes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.