Conduction and Mechanical Properties of Single-Ion Conducting Ionomers

基于极性单体的离聚物是一类重要的能源材料，适用于需要单离子传导的应用。 在这项研究中，正在制造三种新型材料：（1）高分子量可逆加成-断裂链转移（RAFT）离聚物，其是阴离子单体和极性溶剂化单体的无规共聚物，（2）具有一个离聚物无规共聚物导电嵌段和一个结构嵌段的RAFT二嵌段共聚物，和（3）极性低Tg（玻璃化转变温度）非挥发性增塑剂。 通过充分理解RAFT共聚物离聚物的介电和粘弹性响应，将确定用于Li抗衡离子传导的最佳组合物，然后将制备具有相同软嵌段组合物的RAFT二嵌段共聚物。 通过这种方式，可以识别限制到层状或圆柱形相的影响，还可以使用X射线散射来详细描述形态。 这些聚合物的线性粘弹性响应将被理解为使用简单的扩展劳斯和爬行模型，包括离子缔合寿命的影响。 极性低Tg非挥发性增塑剂将被添加到这些材料中，以提高软域的离子电导率和介电常数，同时降低Tg。 到目前为止，具有极性溶剂化侧链的硅氧烷低聚物似乎是最好的，因为它们的T非常低（在-80 ℃和-60 ℃之间）。 通过探索共聚单体和增塑剂的离子含量、极性和比溶剂化能力的参数空间，目标是指导未来能源材料竞技场领域的材料设计。 对于二嵌段共聚物，接近室温的模量也是至关重要的，将测量这些参数变化对模量的影响，以了解离子传导和机械性能之间的权衡，以及它们与形态和每个微相中增塑剂的量的联系。在能源竞技场中，新材料的应用将同时需要一种（且仅一种）离子的高电导率和良好的机械强度。 这项关于聚合物能源材料的离子传导和机械性能的研究旨在了解仅传导一种离子的聚合物的结构-性能关系，例如用于先进电池的锂。开发仅传导锂的锂离子传输材料（与今天电池中使用的锂盐相反的单离子导体，也必须传导带负电荷的离子）的一个强大优势是电池充电和电池电源的访问速度可以快100倍。 如果成功的话，从这项研究中产生的基础知识将导致为各种特定的能源应用设计聚合物材料所需的理解，包括先进的电池，燃料电池，太阳能电池，离子致动器，超级电容器和能量收集设备;其中每一个都需要离子传输和机械强度。 这些应用提供了社会效益，可能会改善地球仪上人类的生活。 此外，该项目将涉及研究生和本科生的教育和培训。

TECHNICAL SUMMARY: Ionomers based on polar monomers are an important class of energy materials for applications that require single-ion conduction. In this research, three novel types of materials are being made: (1) High molecular weight Reversible Addition-Fragmentation chain Transfer (RAFT) ionomers that are random copolymers of an anionic monomer and a polar solvating monomer, (2) RAFT diblock copolymers with one ionomeric random copolymer conducting block and one structural block and (3) polar low-Tg (glass transition temperature) non-volatile plasticizers. By fully understanding the dielectric and viscoelastic response of the RAFT copolymer ionomers, the optimal compositions for conduction of Li counterions will be identified and then RAFT diblock copolymers will be prepared with identical composition of the soft block. In this way, the effects of confinement to lamellar or cylinder phases can be identified, using also X-ray scattering to detail morphology. The linear viscoelastic response of these polymers will be understood using simple extensions of Rouse and reptation models to include the effects of ion association lifetimes. Polar low-Tg non-volatile plasticizers will be added to those materials to boost ion conductivity and dielectric constant of the soft domains, while lowering Tg. Thus far, siloxane oligomers with polar solvating side chains seem best, owing to their very low T (between -80 C and -60 C). By exploring the parameter space of ion content, polarity and specific solvation ability of both the comonomer and the plasticizer, the goal is to guide future materials design in the energy materials arena. For the diblock copolymers the modulus near room temperature is also crucial and the effects of these parameter variations on modulus will be measured to understand the tradeoff between ion conduction and mechanical properties, and their link to morphology and the amount of plasticizer in each microphase.NON-TECHNICAL SUMMARY: Applications that will be enabled by new materials in the energy arena simultaneously require high conductivity of one (and only one) type of ion and good mechanical strength. This research on ion conduction and mechanical properties of polymeric energy materials aims to understand the structure-property relations in polymers that conduct only one type of ion, such as lithium for advanced batteries. One strong advantage of developing materials for lithium ion transport that only conduct lithium (single-ion conductors as opposed to the lithium salts used in batteries today that also must conduct a negatively charged ion) is that both battery charging and access to the power of the battery could be as much as 100 times faster. If successful, the fundamental knowledge generated from this research will result in the understanding needed to design polymeric materials for a variety of specific energy applications, including advanced batteries, fuel cells, solar cells, ionic actuators, supercapacitors and energy harvesting devices; each of which require ion transport and mechanical strength. These applications offer societal benefits that may improve the lives of humans across the globe. Additionally, the project will involve education and training of graduate and undergraduate students.