Ionomer thin films for fuel cells and related applications

尺寸小于人类头发大小的聚合物薄膜的行为与它们的主体材料对应的不同。导电聚合物是这种材料的子类，根据分子结构的不同，它们可以是电子导电的，也可以是离子导电的。离子导电聚合物或离聚体薄膜具有广泛的应用，例如在燃料电池、人工光合作用、传感器、致动器以及作为功能涂层方面。聚合物电解质燃料电池(PEFCs)催化层中的离聚体薄膜由于出人意料的高传质阻力而被认为是导致性能/电压损失的重要原因。如果我们要利用PEFC作为城市车辆零排放动力源的潜力，解决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子材料，这些材料具有简单的质量传输特性。然而，离聚体的分子结构和性能之间缺乏联系，这阻碍了此类材料的设计和开发。在拟议的研究中，加拿大麦克马斯特大学的正电子束设备将使用一种基于科学的方法来揭开质量传输阻力的起源--一些先进的实验技术--其中一项最近才在整个北美获得--。*拟议研究计划的长期目标是指导针对特定应用功能调整的新型离聚体分子的开发，例如在燃料电池、人工光合作用、传感器、致动器、涂层、纳米硫蛋白选择性膜中。这将通过建立离聚体薄膜的结构-性质关系，量化相分离结构和所产生的性质对相关刺激(温度、湿度、电位)的响应，并将其全部与离聚体的分子结构及其与不同化学/物理特性的基质的相互作用相关联来实现。通过研究一些不同的离聚体在分子结构上的不同，该研究计划将离聚体的分子结构与薄膜的结构-性能联系起来。这样的知识目前还不存在。从研究计划中获得的基础知识将为下一代离子材料的设计提供以科学为基础的指导方针，这些材料可针对理想的功能性能进行调整；例如，具有高自由体积的离聚体，即增强了PEFC的传质特性；具有高亲水性界面表面的离聚体，用于轻松吸附传感器用的极性分子(如醇)；具有疏水表面的离聚体薄膜，用于防水防护涂层。衬底-离聚体相互作用的知识将有助于基于薄膜平台的纳米制造。

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.