CAREER: Beyond alignment: novel mechanisms for controlling block copolymer phase behavior using magnetic fields

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。非技术概述：嵌段共聚物(BCP)是由两个或两个以上化学连接的不同分子链块组成的一类材料。这种材料用于药物输送、粘合剂、电池和电子产品。BCP对于开发这些类型的先进材料很有吸引力，因为它们可以通过一种称为自组装的过程自发形成具有明确特征的纳米级结构。然而，为了更广泛地利用BCP的独特性质，它们的大规模自组装和有序化必须得到很好的控制。这项研究旨在揭示利用低强度磁场创造新的BCP结构的新机制，并随后利用这些发现开发具有可调性能的新的BCP材料。在更广泛的背景下，该项目将提供关于利用外部磁场的最小能量将BCP组装和加工成有序材料的新方法的基本知识，有可能为开发比传统加工方法更可持续的先进材料提供一条更可持续的途径。更广泛地说，为了提高材料相关领域的积极性、参与度和后续的预科，该项目还将使用数字工具、包容性的教学和实验室实践、基于研究的课程内容以及带动手演示的实验室之旅，供从高中到研究生的学生使用，特别注重吸引女性和来自有色人种社区的学生。技术摘要：虽然嵌段共聚物(BCP)在开发先进材料方面很有吸引力，但将BCP加工成长程有序材料的实用方法是有限的，因为磁场或电场排列等技术通常不可行，因为所需的场强很大，而且场响应化学物质有限。该项目将确定新发现的弱抗磁性BCP溶液中磁场诱导相形成的机制，这些机制无法用传统的磁畴排列机制来解释，并利用这些发现开发具有大长度有序的新的BCP材料。中心假设认为，低强度磁场主要通过改变聚合物和溶剂的结构和流动性来促进相变。潜在的分子尺度机制将通过一套光谱工具进行研究；磁流变学和小角散射将确定这些分子机制如何在更长的尺度上表现出来。最后，将检查温度、磁场强度和磁化几何形状等工艺参数，以制定精确控制所得相和相关机械性能的指导方针。然后，这种理解将被用于制定选择溶剂、BCP结构和块化学的指南，以增强现场响应性，为开发具有精细性能的有序BCP材料开辟了一种全新的方法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).NON-TECHNICAL SUMMARY:Block copolymers (BCPs) are a class of materials composed of two or more chemically-linked distinct blocks of molecular chains. Such materials are used in drug delivery, adhesives, batteries and electronics. BCPs are attractive for developing these types of advanced materials because they can spontaneously form nanometer-sized structures with well-defined features via a process known as self-assembly. However, to more broadly harness the unique properties of BCPs, their self-assembly and ordering on large lengthscales must be well-controlled. This research aims to uncover new mechanisms underlying creation of new BCP structures using low-intensity magnetic fields, and subsequently harness these findings to develop new BCP materials with tunable properties. In the broader context, this project will provide fundamental knowledge on new methods for assembling and processing BCPs into ordered materials using minimal energy from external fields, potentially providing a more sustainable route for developing advanced materials than traditional processing methods. More broadly, to improve enthusiasm, engagement, and subsequent matriculation in materials-related fields, the project will also employ digital tools, inclusive teaching and lab practices, research-based course content, and lab tours with hands-on demos for students at the high school through graduate levels, with a particular focus on engaging women and students from communities of color.TECHNICAL SUMMARY:While block copolymers (BCPs) are attractive for developing advanced materials, practical methods for processing BCPs into materials with long-range order are limited, as techniques like magnetic or electric field alignment are typically unfeasible due to the large required field strengths and limited field-responsive chemistries. This project will determine the mechanisms underlying newly-discovered magnetic field-induced phase formation in weakly diamagnetic BCP solutions that cannot be explained by traditional mechanisms of domain alignment, and employ these findings to develop new BCP materials with ordering over large lengthscales. The central hypothesis posits that low intensity magnetic fields promote phase transitions primarily by altering the structure and mobility of both polymer and solvent. The underlying molecular-scale mechanisms will be investigated via a suite of spectroscopic tools; magneto-rheology and small angle scattering will then determine how these molecular mechanisms manifest at longer lengthscales. Finally, processing parameters such as temperature, field strength, and magnetization geometry will be examined to develop guidelines for precisely controlling the resulting phase and associated mechanical properties. This understanding will then be used to develop guidelines for selecting solvents, BCP architectures, and block chemistries that enhance field-responsiveness, opening an entirely new approach for developing well-ordered BCP materials with finely-tuned properties..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.