Stability of Complex Phases in Diblock Copolymer Melts

二嵌段共聚物熔体中复杂相的稳定性

• 批准号: 1719692
• 负责人: Kevin Dorfman
• 金额: $ 37.5万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-06-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1719692&HistoricalAwards=false
• 关键词: Stability; Complex; Phases; Diblock; Copolymer

NONTECHNICAL SUMMARYThis award supports computational and theoretical research and education on how polymers, long chain-like molecules, organize themselves into 3D structures more complex than packed spherical balls. AB diblock polymers are formed by chemically bonding together two distinct polymer chains end-to-end. At sufficiently low temperatures, a mixture of polymers A and B will separate into two distinct phases, much the same as the way oil and water separate into two layers when salad dressing sits in the refrigerator. Such macroscopic phase separation is not possible for a melt of diblock polymers; owing to the chemical bond between the two blocks, the furthest the two blocks can separate is the length of the polymer chain. As a result, diblock polymer melts undergo microphase separation into ordered structures with nanometer length scales set by the size of the blocks. The PIs will investigate the microphase separation that occurs for the case where the diblock polymer is compositionally asymmetric, that is when the volume fraction of A is small, and conformationally asymmetric, i.e. where the elasticity of the A block and the B block differ. The compositional asymmetry leads to a system where spheres of A form inside a continuous matrix of B. For decades, it was assumed that the stable ordered state of sphere-forming, microphase separated diblock polymers was a body-centered cubic structure, a type of close-packed structure analogous to that seen in stacks of cannon balls or oranges. Recently, experiments and theory have demonstrated that conformationally asymmetric diblock polymers can also form considerably more complicated packings known as Frank-Kasper and Laves phases. These phases were first seen in metallic alloys, where the atoms have different sizes, and the corresponding phases in diblock polymers involve the packing of spherical particles of different sizes formed by the spontaneous self-assembly of the polymers as they are cooled. This project will determine whether simplified theories based on the geometry of these packings can explain their origin in diblock polymers. Subsequent work will explore the role of the exchange of polymers between different particles, aiming to explain experimental results showing that thermal processing can produce different particle packings. The project aims to develop a connection between the formation of these complex phases in diblock polymers and their emergence in the different context of metallic alloys. Additional broader impacts will emerge from the development of computational tools required to study this problem and their release to the community at large. Graduate students and undergraduate students will receive advance training in polymer physics and, more broadly, materials science through their participation in the research activities of this project. The results will be communicated to the general public through a collated collection of images of complex phases on a dedicated website. These complex phases possess an aesthetic beauty, embodied by the well-known Penrose tiling. The image collection will not only include images of these complex phases generated by the project, but an explanation of their origins in the context of block polymers.TECHNICAL SUMMARYThis award supports computational and theoretical research and education aiming to advance understanding of the stability of complex phase formation in sphere-forming diblock polymers. The research in this project consists of two parts. In the first part, the PIs will assess the ability of geometric theories such as sphericity and the diblock foam model to predict the relative stability of Frank-Kasper and Laves phases in diblock polymers. The results of these calculations will be compared to the predictions from field-theoretical models for diblock polymers. In the second part of the project, the PIs will use dissipative particle dynamics simulations to determine the effect of chain exchange on the transitions between different complex phases during thermal processing of block polymer melts. The field-theoretic results will be included as part of the "Broadly Accessible Self-Consistent Field Theory" website, which includes software for performing these calculations and solved examples emerging from research projects using the software. These computational results will be combined with data-processing tools to produce slices through various planes, which will provide the image collection for the public outreach component of the project.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.

非技术摘要该奖项支持关于聚合物（长链状分子）如何将自身组织成比填充球形球更复杂的 3D 结构的计算和理论研究和教育。 AB 二嵌段聚合物是通过将两个不同的聚合物链首尾相连地化学键合在一起而形成的。在足够低的温度下，聚合物 A 和 B 的混合物将分离成两个不同的相，这与沙拉酱放在冰箱中时油和水分离成两层的方式非常相似。对于二嵌段聚合物的熔体来说，这种宏观相分离是不可能的；由于两个嵌段之间的化学键，两个嵌段可以分开的最远距离是聚合物链的长度。结果，二嵌段聚合物熔体经历微相分离，形成有序结构，其纳米长度尺度由嵌段尺寸决定。 PI 将研究在二嵌段聚合物组成不对称（即 A 的体积分数较小）和构象不对称（即 A 嵌段和 B 嵌段的弹性不同）的情况下发生的微相分离。组成的不对称性导致了一个系统，其中 A 的球体在 B 的连续基质内形成。几十年来，人们一直认为球体形成、微相分离的二嵌段聚合物的稳定有序状态是体心立方结构，这是一种类似于炮弹或橙子堆叠中看到的密堆积结构。最近，实验和理论表明，构象不对称二嵌段聚合物也可以形成相当复杂的堆积，称为 Frank-Kasper 和 Laves 相。这些相首先出现在金属合金中，其中原子具有不同的尺寸，二嵌段聚合物中的相应相涉及不同尺寸的球形颗粒的堆积，这些颗粒是由聚合物在冷却时自发自组装形成的。该项目将确定基于这些填料几何形状的简化理论是否可以解释它们在二嵌段聚合物中的起源。后续工作将探讨不同颗粒之间聚合物交换的作用，旨在解释热处理可以产生不同颗粒堆积的实验结果。该项目旨在建立二嵌段聚合物中这些复杂相的形成与它们在金属合金的不同背景下出现之间的联系。研究这个问题所需的计算工具的开发以及向整个社区的发布将产生更广泛的影响。研究生和本科生将通过参与该项目的研究活动，接受高分子物理学以及更广泛的材料科学方面的高级培训。结果将通过专门网站上整理的复杂阶段图像集合向公众传达。这些复杂的阶段具有美感，著名的彭罗斯瓷砖就体现了这一点。该图像集不仅包括该项目生成的这些复杂相的图像，还包括它们在嵌段聚合物背景下的起源解释。技术摘要该奖项支持计算和理论研究和教育，旨在增进对球形二嵌段聚合物中复杂相形成稳定性的理解。本项目的研究由两部分组成。在第一部分中，PI 将评估几何理论（例如球形度和二嵌段泡沫模型）预测二嵌段聚合物中 Frank-Kasper 和 Laves 相相对稳定性的能力。这些计算的结果将与二嵌段聚合物场论模型的预测进行比较。在该项目的第二部分中，PI 将使用耗散粒子动力学模拟来确定嵌段聚合物熔体热加工过程中链交换对不同复杂相之间转变的影响。场论结果将作为“广泛可访问的自洽场论”网站的一部分包含在内，该网站包括用于执行这些计算的软件以及使用该软件的研究项目中出现的解决示例。这些计算结果将与数据处理工具相结合，产生不同平面的切片，这将为该项目的公共外展部分提供图像收集。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Laves Phase Field in a Diblock Copolymer Alloy

• DOI: 10.1021/acs.macromol.2c00346
• 发表时间: 2022-03
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Benjamin R. Magruder;So Jung Park;Ryan P. Collanton;F. Bates;K. Dorfman

Interfacial geometry in particle-forming phases of diblock copolymers

• DOI: 10.1103/physrevmaterials.6.015602
• 发表时间: 2022-01
• 期刊: Physical Review Materials
• 影响因子: 3.4
• 作者: Ryan P. Collanton;K. Dorfman

Complex Phase Behavior in Particle-Forming AB/AB′ Diblock Copolymer Blends with Variable Core Block Lengths

• DOI: 10.1021/acs.macromol.1c01290
• 发表时间: 2021-08
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: A. Lindsay;G. K. Cheong;Austin J. Peterson;S. Weigand;K. Dorfman;T. Lodge;F. Bates

Symmetry breaking in particle-forming diblock polymer/homopolymer blends

• DOI: 10.1073/pnas.2006079117
• 发表时间: 2020-07-21
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Cheong, Guo Kang;Bates, Frank S.;Dorfman, Kevin D.
• 通讯作者: Dorfman, Kevin D.

Simulations of sphere-forming diblock copolymer melts

• DOI: 10.1103/physrevmaterials.6.095602
• 发表时间: 2022-09
• 期刊: Physical Review Materials
• 影响因子: 3.4
• 作者: A. Chawla;F. Bates;K. Dorfman;D. Morse