Phase Transition Kinetics and Dynamics of Block Copolymers in Selective Solvents

技术综述：嵌段共聚物在选择性溶剂中表现出自组装纳米结构域形状的变化和有序相对称性的变化。虽然有许多关于嵌段共聚体系中溶剂介导的相互作用的平衡相图和热力学的研究，但对转化的动力学和动力学了解较少。特别是，人们对相变动力学的压力依赖性知之甚少。本研究的主要目的是(I)利用基于时间分辨同步加速器的小角X射线散射，研究选择性溶剂中嵌段共聚物的相变机理与有序-无序和有序-有序相变动力学的压力依赖性，以及(Ii)利用X射线强度起伏光谱研究纳米尺度下嵌段共聚物链的内部动力学。X射线散射研究将得到其他实验技术的补充，包括小角中子散射、原子力显微镜、动态光散射和流变学。压力跳跃测量特别适合于检查转换过程的早期阶段。为了获得对潜在物理机制的详细了解，将开发用于分析散射数据的分子动力学模拟和模型。非技术摘要：由两种或两种以上化学上不同的聚合物不可分离地结合在一起的嵌段共聚物组成的解决方案和凝胶具有广泛的应用范围，从消费品到制药和其他应用的新型材料。本文提出的研究在高环境压力下嵌段共聚材料的使用方面具有潜在的应用，例如石油钻井中的嵌段共聚材料。在以嵌段共聚为基础的产品的制造中，压力也可以用作控制制造过程的一种手段。该项目将为研究生和本科生提供跨学科的实践培训，从而有助于未来科学家的发展。学生们还将在国家实验室学习使用最先进的同步加速器X射线仪器。将特别强调采用最佳做法，通过与波士顿大学科学和工程专业妇女小组(WISE)密切互动，招募、培训和指导各级女学生。资深教师将向更广泛的受众展示这些工作，并参与旨在吸引和指导高中生和大学生追求科学和工程职业的外展项目。与捷克共和国研究人员的国际合作是该计划不可或缺的一部分。这一合作为美国学生和高级研究人员提供了从欧洲正在开发的专业知识中受益的机会，特别是在基于同步加速器的软物质和聚合物物理领域。

TECHNICAL SUMMARY:Block copolymers in selective solvents exhibit simultaneous change in the shape of self-assembled nanoscale domains along with a change in the symmetry of the ordered phases. While there are many studies of the equilibrium phase diagrams and thermodynamics of solvent mediated interactions in block copolymer systems, the dynamics and kinetics of transformations are less well understood. In particular, not much is known about the pressure dependence of transformation kinetics. The primary goal of the research proposed here is (i) to examine the pressure dependence of phase transition mechanisms and the kinetics of order-disorder and order-order phase transitions in block copolymers in selective solvents, using time-resolved synchrotron based small angle x-ray scattering, and (ii) the internal dynamics of the block copolymer chains in the nanoscale domains using X-ray Intensity Fluctuation Spectroscopy. The x-ray scattering studies will be complemented by other experimental techniques, including small angle neutron scattering, atomic force microscopy, dynamic light scattering and rheology. Pressure jump measurements are particularly suitable for examining the early stages of the transformation processes. To obtain detailed insight into the underlying physical mechanisms, Molecular Dynamics simulations and models for analyzing the scattering data will be developed.NON-TECHNICAL SUMMARY:Solutions and gels made up of block copolymers that inseparably combine two or more chemically distinct polymers have broad range of applications from consumer products to novel materials for pharamaceutical and other applications. The research proposed here has potential applications in the use of block copolymer materials at high ambient pressure, such as those involved in oil drilling. Pressure can also be used as a means to control fabrication processes in the manufacture of block copolymer based products. The project will provide interdisciplinary, hands-on training to graduate and undergraduate students, and thus contribute to the development of future scientists. The students will also learn to use state-of-the art synchrotron based x-ray instrumentation at National Laboratories. Special emphasis will be made to incorporate best practices to recruit, train and mentor women students at all levels by interacting closely with Women in Science and Engineering (WISE) group at Boston University. The senior faculty will present the work to a broader audience, and participate in outreach programs designed to attract and mentor high school and college students to pursue science and engineering careers. An international collaboration with researchers in Czech Republic is an integral part of this program. This collaboration provides opportunities to US students and senior researchers to benefit from the expertise that is being developed in Europe, particularly in the area of synchrotron- based soft matter and polymer physics.