Phase Transitions and Dynamics in Block Copolymers

嵌段共聚物的相变和动力学

• 批准号: 1310436
• 负责人: David Morse
• 金额: $ 30万
• 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: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1310436&HistoricalAwards=false
• 关键词: Phase; Transitions; Dynamics; Block; Copolymers

Technical SummaryThis award supports computational studies of the equilibrium behavior and dynamics of block copolymer materials aimed to identify universal behavior. Understanding the equilibrium behavior of these materials has long been based on various forms of self-consistent-field theory. The self-consistent-field approximation is valid in the limit of very long, very strongly overlapping polymers, but neglects strong collective correlations that have very important effects for shorter, more strongly interacting polymers. More sophisticated coarse-grained theories beyond self-consistent-field approximations yield predictions for all physical properties that depend upon the degree of overlap, as quantified by a dimensionless parameter. Simulations of the disordered phase of diblock copolymers have confirmed the predicted existence of systematic, universal behavior of the structure factor that can now be quantitatively described by recently developed theories. Two research thrusts supported by this award will build upon this progress in different ways.The first thrust is a comprehensive computational study of the parameter dependence of phase boundaries in diblock copolymer melts, using graphics processor unit accelerated simulations and free energy methods to precisely identify phase boundaries. This project aims to use simulation to produce a universal phase map for finite diblock copolymers. This will generalize the phase map in a manner that should allow accurate quantitative predictions of phase boundaries even for short, strongly interacting diblock copolymers. Distinctive features of this approach include development of more sophisticated methods for analyzing simulation results in order to minimize ambiguities that arise from imperfect knowledge of the phenomenological Flory-Huggins interaction parameter.The second thrust focuses on the use of simulations to study collective dynamical phenomena in diblock copolymer melts. Specifically, it will address collective dynamics in the disordered phase near the order-disorder transition, and the dynamics and mechanisms of order-disorder and order-order transitions. The research supported by this award will provide opportunities for training graduate students in cutting edge computational and theoretical methods in an environment that provides rich exposure to experimental aspects of polymer science. This award also supports the development, documentation, and dissemination of open source computational software for both particle-based simulations and self-consistent field calculations, which contributes to the cyberinfrastructure of the soft-materials research community.Nontechnical Summary This award supports computational studies aimed to advance understanding of materials made from long chain-like molecules, polymers. Block copolymers are polymers comprised of linear blocks or subchains of different chemistry. A linear polymer chain, that contains two such blocks, of A and B monomers, bonded together by their ends forming a bigger chain (AB), is called a diblock copolymer. At temperatures at which mixtures of liquids composed of pure A and pure B chains would still be a liquid, diblock copolymers form periodically ordered structures. Spontaneous formation of these periodic structures is driven by the tendency of different blocks to phase separate, and by the fact that macroscopic phase separation is suppressed by the covalent linkage of the two blocks with each other. These ordered structural materials found applications as membranes for water purification, and as template materials for microelectronics and storage devices. Studies suggest that diverse kinds of diblock copolymers display nearly identical behavior when interpreted in the correct way. This award supports research aimed to advance fundamental understanding of diblock copolymer materials and would contribute to the ability to design new diblock copolymer materials with desired properties for new applications.The PI will investigate whether much more accurate predictions might be possible for real systems by quantifying how the behavior seen in computer simulations depends on interactions between chains. A primary goal of this research is to use computer simulations to generate a map of structural transformations as related to chemical structure and chain interactions. This award also supports the development, documentation, and dissemination of open source software that contributes to the cyberinfrastructure of the soft-materials research community.

该奖项支持对嵌段共聚物材料的平衡行为和动力学进行计算研究，旨在确定普遍行为。 理解这些材料的平衡行为长期以来一直基于各种形式的自洽场理论。自洽场近似是有效的限制非常长，非常强烈的重叠聚合物，但忽略了强大的集体相关性，有非常重要的影响较短，更强的相互作用的聚合物。超越自洽场近似的更复杂的粗粒度理论产生了对所有物理性质的预测，这些物理性质取决于重叠的程度，如由无量纲参数量化的。无序相的二嵌段共聚物的模拟已经证实了预测的存在系统的，普遍的行为的结构因子，现在可以定量描述最近发展的理论。 该奖项支持的两个研究重点将以不同的方式建立在这一进展的基础上。第一个重点是对二嵌段共聚物熔体中相边界的参数依赖性进行全面的计算研究，使用图形处理器单元加速模拟和自由能方法精确识别相边界。本计画的目的是利用模拟的方法来制作有限二嵌段共聚物的通用相图。 这将概括的相图的方式，应该允许准确的定量预测相边界，即使是短，强烈相互作用的二嵌段共聚物。 这种方法的显着特点包括开发更复杂的方法来分析模拟结果，以尽量减少歧义，从不完善的知识的现象学的Flory-Huggins相互作用parameter.The第二个推力集中在使用模拟研究集体动力学现象在二嵌段共聚物熔体。具体来说，它将解决集体动力学在无序相附近的有序-无序过渡，和有序-无序和有序-有序过渡的动力学和机制。该奖项支持的研究将为研究生提供培训机会，使其在提供丰富的聚合物科学实验方面的环境中掌握尖端的计算和理论方法。 该奖项还支持用于粒子模拟和自洽场计算的开源计算软件的开发、记录和传播，为软材料研究社区的网络基础设施做出贡献。非技术性总结该奖项支持旨在促进对长链状分子聚合物材料的理解的计算研究。嵌段共聚物是由不同化学性质的线性嵌段或子链组成的聚合物。含有两个这样的A和B单体嵌段的线性聚合物链，通过它们的末端键合在一起形成更大的链（AB），称为二嵌段共聚物。在由纯A链和纯B链组成的液体混合物仍为液体的温度下，二嵌段共聚物形成周期性有序结构。这些周期性结构的自发形成是由不同嵌段相分离的趋势驱动的，并且由宏观相分离被两个嵌段彼此的共价键抑制的事实驱动。这些有序的结构材料可用作水净化的膜，以及微电子和存储设备的模板材料。 研究表明，不同种类的二嵌段共聚物显示出几乎相同的行为时，以正确的方式解释。该奖项支持旨在推进对二嵌段共聚物材料的基本理解的研究，并将有助于设计具有新应用所需性能的新二嵌段共聚物材料的能力。PI将通过量化计算机模拟中看到的行为如何取决于链之间的相互作用，研究是否可能对真实的系统进行更准确的预测。本研究的主要目标是使用计算机模拟生成与化学结构和链相互作用相关的结构转化图。 该奖项还支持开源软件的开发、记录和传播，为软材料研究社区的网络基础设施做出贡献。