Directed Self-Assembly of Block Copolymers Under Dynamic and Orthogonal Fields

技术概述：从技术角度来看，控制自组装嵌段共聚物（bcp）的顺序是公认的。与此同时，对bcp在外场作用下进行自组装的复杂场-物质相互作用和动力学的理解并不完全。该项目的总体目标是建立一个知识体系，通过应用外场来实现对BCP纳米结构的取向和位置顺序的高保真控制，并了解这种作用的机制。具体来说，这项工作涉及：(1)使用强度和方向随时间和/或位置而变化的磁场，即所谓的动态场；(2)使用多个外场，其中磁场沿垂直方向作用，即所谓的正交场。这项工作将通过开发新的材料和方法来完成，这些材料和方法可以在磁场下实现bcp的快速双轴对准，并将多个场有效地耦合到单个系统中。将设计和合成显示顺磁行为和/或双轴顺序的新型bcp，以实现快速的双轴对齐。利用纳米粒子对外加磁场进行局部扰动的新方法将被开发出来。设备将被设计成能够研究在剪切和磁场同时作用下的自组装。具体目标是：(1)开发具有双轴有序和顺磁性的bcp；(2)开发和研究动态磁场定向自组装；(3)研究正交磁场和流场下的定向自组装。嵌段共聚物是技术上重要的一类合成材料，由两种或两种以上不同类型的聚合物分子相互连接而成。根据每种聚合物分子的化学性质，所得到的材料由尺寸约为3-100纳米的规则排列的结构组成。从技术角度来看，控制这些结构的位置和排列的能力是非常可取的。引人注目的例子包括这种排列嵌段共聚物在发电（例如光伏）和水净化方面的应用。该项目解决了目前在利用电场或磁场等外部场对嵌段共聚物材料进行排列的能力和基本理解方面的差距。因此，它能够影响或促进具有上述社会影响的广泛技术。该项目涉及广泛的影响，包括本科生和研究生的课程开发，通过科学博览会和科学之路项目开展的K-12外展活动，以及与科学教师的暑期研究项目。PI将与其他利益攸关方合作，着手采取具体举措，改善对代表性不足群体的招聘。

TECHNICAL SUMMARYThe need to control order in self-assembled block copolymers (BCPs) is well recognized from a technological perspective. At the same time, there is incomplete understanding of the complex field-matter interactions and dynamics with which BCPs undergo self-assembly under the action of external fields. The overall objective of this project is to build a body of knowledge that enables high fidelity control of orientational and positional order of BCP nanostructures by the application of external fields and to understand the mechanisms of such action. Specifically, this work pertains to: (1) the use of magnetic fields which vary in their intensity and direction and a function of time and/or location, so called dynamic fields, and (2) the use of more than one external field where the fields act along perpendicular directions, so called orthogonal fields. This work will be accomplished by the development of new materials and methods which permit fast biaxial alignment of BCPs under magnetic fields and effective coupling of multiple fields to a single system. New BCPs that display paramagnetic behavior and/or biaxial order will be designed and synthesized, to enable fast, biaxial alignment. New methods will be developed based on local perturbation of external magnetic fields using nanoparticles for dynamic field studies. Apparatus will be designed to enable studies of self-assembly under the simultaneous action of shear and magnetic fields.The specific objectives are: (1) development of BCPs that exhibit biaxial order and paramagnetic properties, (2) development and study of dynamic magnetic field-directed self-assembly, and (3) investigation of directed self-assembly under orthogonal magnetic and flow fields.NON-TECHNICAL SUMMARYBlock copolymers represent a technologically important class of synthetic materials and are made up of two or more different types of polymer molecules connected to each other. Depending on the chemical nature of each of the polymer molecules, the resulting materials consist of regularly arranged structures having dimensions of around 3-100 nanometers. The ability to control the position and alignment of these structures is highly desirable from a technological perspective. Compelling examples include applications of such aligned block copolymers for energy generation (e.g. photovoltaics) and water purification. This project addresses current gaps both in capability and fundamental understanding of alignment of block copolymer materials using external fields such as electric or magnetic. As such, it is in a position to impact or facilitate a broad spectrum of technologies with societal impact such as those mentioned above. This project involves a wide range of broader impacts including curriculum development for undergraduate and graduate students, K-12 outreach activities through Science Fair and Science Pathways programs, and summer research projects with science teachers. The PI will embark on specific initiatives aimed at improving recruitment of under-represented groups in collaboration with other stakeholders.