Miscible Blend Dynamics

9629901科尔比这笔赠款将探索聚合物共混物的动力学和流变学领域。最近的实验表明，可混溶共混物具有复杂的流变性。这方面的一个表现是经验时间-温度叠加原理的崩溃，众所周知，该原理对均聚体系是有效的。最近的理论表明，共混物的热流变复杂性是由浓度波动和各组分玻璃化转变温度的差异在链段水平上驱动的。这项研究的实验部分的目标是仔细测量浓度波动(使用小角中子散射)、局部分段动力学(使用介电光谱)和终端动力学(使用前向反冲光谱扩散测量和线性粘弹性)，以系统地测试所提出的在可混相混合物中浓度波动和动力学之间的关系。拟议工作的理论部分将扩展以前的浓度波动思想，即目前仅在分段水平上建模动力学，以预测末端动力学(整个链的松弛)。计算机模拟也将被用来阐明不同变量在可混溶混合物动力学中的作用。%由于聚合物共混物在实际应用中的使用越来越多，因此对其流变性进行定量了解以帮助其加工是很重要的。长期的目标是开发一个完整的分子模型来研究可混溶聚合物共混物的流变性。***

9629901 Colby This grant will explore the area of dynamics and rheology in polymer blends. Recent experiments have shown that miscible blends have complex rheology. One manifestation of this is the breakdown of the empirical time-temperature superposition principle, known to be valid for homopolymer systems. Recent theory suggests that the themorheological complexity in blends is driven at the segmental level by concentration fluctuations, coupled to differences in the glass transition temperatures of the components. The goal of the experimental portion of the proposed research is to carefully measure concentration fluctuations (using small angle neutron scattering), local segmental dynamics (using dielectric spectroscopy) and terminal dynamics (using forward recoil spectroscopy diffusion measurements and linear viscoelasticity) to systematically test the proposed relation between concentration fluctuations and dynamics in miscible blends. The theoretical component of the proposed work will extend previous concentration fluctuation ideas, which currently only model dynamics at the segmental level, to predict terminal dynamics (relaxation of entire chains). Computer simulations will also be used to elucidate the role of different variables in the dynamics of miscible blends. %%% Since polymer blends are seeing increased use in practical applications, it is important that a quantitative understanding of their rheology be obtained so as to assist in their processing. The long-term goal is to develop a complete molecular model forlthe rheology of miscible polymer blends. ***