Ionomer thin films for fuel cells and related applications

聚合物薄膜的尺寸小于一千人的头发大小的行为不同于他们的散装材料对应。导电聚合物是这类材料的子类，根据分子结构，它们可以是电子导电的或离子导电的。离子传导聚合物或离聚物的薄膜具有多种应用，例如在燃料电池、人工光合作用、传感器、致动器中以及作为功能涂层。聚合物电解质燃料电池（PEFC）的催化剂层中的离聚物薄膜已被确定为由于出乎意料的高传质阻力而导致的显著性能/电压损失的来源。如果我们要利用PEFC作为城市车辆零排放电源的潜力，克服这个问题现在被认为是使PEFC负担得起的关键。这个问题的答案是设计下一代离聚物材料，具有容易的质量传输特性。然而，离聚物分子结构与其性能之间缺乏联系，阻碍了此类材料的设计和开发。在拟议的研究中，将使用一种基于科学的方法来解开质量传输阻力的起源，一些先进的实验技术-其中之一最近才在整个北美-加拿大麦克马斯特大学的正电子束设施。拟议的研究计划的长期目标是指导新的离聚物分子的开发，以适应特定的应用功能，例如燃料电池，人工光合作用，传感器，致动器，涂层，纳米选择性膜。这将通过建立离聚物膜的结构-性质关系，量化相分离结构和所得性质如何响应相关刺激（温度、湿度、电位），并将其全部与离聚物的分子结构及其与化学/物理特性不同的基材的相互作用联系起来来实现。通过研究一些不同的离聚物在其分子结构上的变化，研究计划将把离聚物的分子结构与膜的结构-性能联系起来。这种知识目前还不存在。从研究计划中获得的基础知识将为下一代离聚物材料的设计提供基于科学的指导方针，这些离聚物材料具有理想的功能特性;例如，具有高自由体积的离聚物，即增强PEFC的质量传输特性;具有高度亲水界面的离聚物，便于吸附极性分子用于传感器应用的离聚物膜（例如酒精）;用于防水保护涂层的具有疏水表面的离聚物膜。对基底-离聚物相互作用的了解将有利于基于薄膜平台的纳米织物。

Polymer thin films with dimensions less than one-thousands the size of human hair behave differently than their bulk material counterpart. Conducting polymers are sub-class of this material group and depending on the molecular architecture, they can be either electron-conducting or ion-conducting. Thin films of ion-conducting polymers or ionomers find a variety of applications, e.g. in fuel cells, artificial photosynthesis, sensors, actuators, and as functional coatings. The ionomer thin films in the catalyst layers of polymer electrolyte fuel cells (PEFCs) have been identified as a source of significant performance/voltage loss due to unexpectedly high mass transport resistance. Overcoming this problem is now considered critical to making the PEFCs affordable, if we are to harness its potential as zero-emissions power source for urban vehicles. The answer to the problem is designing next generation ionomer materials that possess facile mass transport characteristics. However, the lack of relationship between ionomer molecular structure and its properties is hampering the design and development of such materials. In the proposed research will use a science-based approach for unraveling the origin of the mass transport resistance some advanced experimental techniques - one of which has only recently become available in whole of North America - the Positron Beam Facility at McMaster University, Canada. The long-term objective of the proposed research program is to guide the development of new ionomer molecules tuned for application-specific functionalities, e.g. in fuel cells, artificial photosynthesis, sensors, actuators, coatings, nanothin selective membranes. This will be achieved by establishing structure-property relationships of ionomer films, quantifying how the phase-segregated structure and resulting properties responds to pertinent stimuli (temperature, humidity, potential), and link it all to the molecular architecture of ionomer and its interactions with substrates varying in chemical/ physical characteristics. By studying a number of different ionomer varying in their molecular architecture, the research program will link the molecular architecture of the ionomers to the film structure-property. Such a knowledge currently does not exist. The fundamental knowledge created from the research program will provide science-based guidelines for the design of next-generation ionomer materials tuned for desirable functional properties; e.g. ionomers with high free volume, i.e. enhanced mass transport characteristics for PEFCs; ionomers with highly hydrophilic interfacial surface for facile sorption of polar molecules (e.g. alcohol) for sensor applications; ionomer films with hydrophobic surface for water-repellant protective coatings. Knowledge on substrate-ionomer interaction will benefit nanofabrication based on thin film platform.