Dynamics in Miscible Polymer Systems

多组分体系中的聚合物表现出复杂的动力学。对这些动力学的理解应该有助于预测可混溶聚合物混合物的流变性。提出了一些实验，探讨了混合对一些可混溶聚合物体系动力学的影响。在所有情况下，将使用核磁共振弛豫时间测量来表征这些混合物中单个组分的分段动力学。对于一些系统，这些测量将由合作者执行的工作(节段动力学的固态核磁共振测量、扩散测量和计算机模拟)来补充。要研究的具体体系包括聚丁二烯/聚乙烯共混物、聚苯乙烯和聚异戊二烯的低相对分子质量共混物、两种不同相对分子质量聚苯乙烯的同位素共混物、以聚苯乙烯为稀释组分的一系列共混物、聚环氧乙烷和聚乙烯基酚的共混物，以及苯乙烯-异戊二烯嵌段共聚物。总而言之，这些活动将把混合动力学的宏观测量与微观模拟结合起来。需要解决的具体问题包括相容共混物中不同组分动力学的微观起源、链段动力学的预测以及链段动力学和末端动力学之间的关系。如果拟议的工作得到资助，我们基于均聚物性质预测共混动力学和流变学的能力有望取得重大进展。这项工作的影响将超出可混溶聚合物共混领域。要了解聚合物与纳米材料或生物结构的复合材料的性质，需要对附近的链段或表面如何影响聚合物动力学有深入的了解。这里提出的实验和模拟之间的详细比较提供了对模拟潜力的敏感测试，并将导致改进的潜力，这将对生物学、其他材料领域和其他领域的模拟产生积极影响。这项提议的资金还将促进对研究生和K-12级学生的培训。如果这项提议得到资助，那些受支持的人将帮助威斯康星大学麦迪逊分校为高二学生举办一项暑期教育活动(并为其完善课程)。这项为期三周的活动是一个更大的项目的一部分，面向那些原本不太可能上大学的学生。

Polymers in multicomponent systems exhibit complex dynamics. An understanding of these dynamics should lead to the ability to predict the rheological properties of miscible polymer mixtures. Experiments that probe the influence of mixing on dynamics in a number of miscible polymer systems are proposed. In all cases, NMR relaxation time measurements will be used to characterize the segmental dynamics of individual components in these mixtures. For some systems, these measurements will be supplemented by work performed by collaborators (solid-state NMR measurements of segmental dynamics, diffusion measurements, and computer simulations). Specific systems to be studied include polybutadiene/poly(vinyl ethylene) blends, low molecular weight blends of polystyrene and polyisoprene, isotopic blends of two different molecular weight polystyrenes, a series of blends containing polystyrene as a dilute component, blends of poly(ethylene oxide) and poly(vinyl phenol), and styrene-isoprene block copolymers. Together, these activities will couple macroscopic measurements of blend dynamics at both the segmental and terminal level with microscopic simulations. Specific issues to be addressed include the microscopic origin of distinct component dynamics in miscible blends, the prediction of segmental dynamics, and the relationship between segmental and terminal dynamics. If the proposed work is funded, significant progress in our ability to predict blend dynamics and rheology based upon homopolymer properties is anticipated. This work will have impact beyond the field of miscible polymer blends. Insights obtained about how nearby segments or surfaces impact polymer dynamics will be required for understanding the properties of composites of polymers with nanomaterials or biological structures. The detailed comparisons between experiment and simulation proposed here provide a sensitive test of the simulation potentials and will lead to improved potentials that will positively impact simulations in biology, other materials areas, and beyond. The funding of this proposal would also advance the training of both graduate students and students at the K-12 level. If this proposal is funded, those supported will help run (and refine the curriculum for) a summer education activity at the University of Wisconsin Madison for high school sophomores. This three-week activity is part of a larger program for students who otherwise would be unlikely to go to college.