UNS: Interfacial Behavior and Thermodynamics of Block Copolymer Directed Self-Assembly

1512517 -Henderson一种特殊形式的聚合物，可以定制为具有非常独特的性能，通常被称为嵌段共聚物。嵌段共聚物通过简单地将两种不同类型的聚合物链连接在一起而制成。 由于不同类型的聚合物不喜欢混合，就像油和水分离一样，两种不同的聚合物链或嵌段也试图彼此分离，但只能以与聚合物分子的长度尺度相当的距离分开，因为它们键合在一起。 这自然会产生具有纳米长度尺度的结构和秩序的材料。 这些相分离和有序的嵌段共聚物可以具有非常独特的性能，因为这种微米和纳米结构。 这种有序嵌段共聚物的一个有趣且重要的应用是作为用于制造用于构建微芯片的纳米尺度特征的模板。 该项目将开发有关在这种嵌段共聚物中发生的自组装过程的基础知识，以允许设计用于制造下一代微芯片和其他有序纳米结构材料的材料和工艺。 使用嵌段共聚物微相分离来形成具有受控纳米级形态的聚合物薄膜为包括半导体制造、燃料电池和蓄电池以及太阳能在内的不同领域中的问题提供了潜在的解决方案。 定向自组装（DSA）方法提供了使用嵌段共聚物薄膜与异质图案化界面的相互作用来引导嵌段共聚物微相组装成具有长程有序的期望取向的可能性。 虽然迄今为止的大多数工作都集中在具有类似嵌段性质的“对称”嵌段共聚物（例如PS-b-PMMA）上，但具有较大内聚能差异（即高聚合物Flory-Huggins χ值）的嵌段共聚物对于实现具有较小特征尺寸的微相分离形态是有意义的。 这种“不对称”嵌段共聚物及其相行为尚未得到很好的理解。在这个项目中，一个新的介观尺度的分子动力学模型，可以准确地再现具有不对称嵌段相互作用的现实嵌段共聚物的性能和行为，将被用来了解这种材料的本体和薄膜行为，特别是相对于DSA应用。 通过将模型结果与高chi嵌段共聚物薄膜DSA系统的实验数据进行比较，验证了该建模工作。 本论文的主要研究成果包括：（1）建立了快速、有效的嵌段共聚物薄膜行为预测工具;（2）阐明了聚合物组成、嵌段能量、界面组成、界面结构、膜厚等因素对嵌段共聚物微相分离薄膜形态和性能的影响。这项活动的广泛社会影响包括：（1）形成方法和数据的基础，所述方法和数据使得能够对用于从水分离到有机光致发光的一系列领域的嵌段共聚物薄膜材料进行一般设计，（2）推进用于制造下一代集成电路的DSA图案化方法的开发，（3）开发用于嵌段共聚物的计算材料建模工具，（4）在本科和研究生阶段加强代表性不足的少数民族科学和工程教育，（5）培训K-12科学教师，（6）通过童子军和童子军NOVA计划对K-12学生进行STEM教育。

1512517 - HendersonA special form of polymer that can be tailored to have very unique properties is commonly referred to as a block copolymer. Block copolymers are made by simply joining two different types of polymer chains together. Since different types of polymers do not like to mix, much like oil and water separate, the two different polymer chains or blocks also try to separate from one another but can only move apart at distances comparable to the length scale of the polymer molecules since they are bonded together. This naturally gives rise to materials possessing structure and order at nanometer length scales. These phase separated and ordered block copolymers can have very unique properties because of this micro- and nanostructure. One interesting and important application for such ordered block copolymers is as templates for making the nanometer scale features used to build microchips. This project will develop the fundamental knowledge about the self-assembly process that occurs in such block copolymers to allow materials and processes to be designed for manufacturing next generation microchips and other ordered nanostructured materials. The use of block copolymer micro-phase separation to form polymer thin films with controlled nanoscale morphologies offers potential solutions to problems in diverse fields, including semiconductor manufacturing, fuel cells and batteries, and solar energy. Directed self-assembly (DSA) methods offer the possibility to use the interaction of a block copolymer thin film with heterogenous patterned interfaces to guide assembly of the block copolymer microphases into desired orientations with long range order. While most work to date has focused on "symmetric" block copolymers with similar block properties (e.g. PS-b-PMMA), block copolymers that possess large differences in their cohesive energy differences (i.e. high polymer Flory-Huggins chi values) are of interest to achieve micro-phase separated morphologies with smaller feature sizes. Such "asymmetric" block copolymers and their phase behavior are not yet well understood. In this project, a new meso-scale molecular dynamics model that can accurately reproduce the properties and behavior of realistic block copolymers possessing asymmetric block interactions will be used to understand the bulk and thin film behavior of such materials, particularly with respect to DSA applications. This modeling work will be validated by comparison of model results with experimental data from high chi block copolymer thin film DSA systems. The intellectual merits of the proposed work can broadly be defined as: (1) establishment of fast and efficient tools for predicting behavior of block copolymer films, (2) elucidation of the impact of factors such as polymer composition and block energetics, interface composition and structure, and film thickness on the morphology and properties of microphase separated block copolymer thin films. The broader societal impacts of this activity include: (1) forming the foundation of methods and data that enable general design of block copolymer thin film materials for a range of fields from water separation to organic photovoltaics, (2) advancing the development of DSA patterning methods for fabrication of next generation integrated circuits, (3) developing computational material modeling tools for block copolymers, (4) enhancing under-represented minority education in science and engineering at the undergraduate and graduate level, (5) training of K-12 science teachers, and (6) STEM education K-12 students through the Cub Scout and Boy Scout NOVA program.