FRG: Synthesis, Characterization, and Simulation of Tailored Inhomogeneous Elastomers

智力优势。近年来，在理解结构对由中性柔性聚合物链组成的均质弹性体的物理性质的作用方面取得了很大进展。精心定制的合成，物理测量的新分析，和新的计算机模拟方法已经开发出来，研究这些聚合物网络。现在可以解决更具有挑战性的任务，了解非均匀弹性体的性能。已知或预期不连续相（由自发形成或有意引入的微区组成）的存在会显著影响网络的机械性能。这种情况的两个例子是在离聚物中形成的极性域和在双峰网络中形成的致密交联域。两种类型的非均匀弹性体将通过合成模型系统，将允许使用NMR，X射线和中子散射测量所观察到的性能的分子基础的识别进行研究。这些系统的计算机模拟将提供与实验结果的比较。具体的研究领域包括：1）在主链上沿着以规则间隔带有相互作用基团的聚硅氧烷前体链的流动性质; 2）由这些前体链合成的端连接网络的宏观和微观性质以及与实验结果比较的动力学和平衡Monte Carlo模拟的发展; 3）研究双峰网络的性质，以测试最近提出的预测短链聚集的发生的标度，短链聚集显著影响弹性体的性质。 更广泛的影响。待研究的特定材料在导电弹性体（在离聚物网络的情况下）和高强度橡胶纤维（在双峰网络的情况下）领域中具有潜在的应用。科学成果将通过专业会议和康奈尔材料研究中心组织的工业推广计划进行传播。研究生和本科生都将参与该项目;他们将特别了解聚合物和弹性体的合成以及化学和物理性质。他们将获得对实验分析和计算机模拟的耦合的普遍赞赏，这对工业越来越重要，因为被设计用于造福社会的材料变得更加复杂。

Intellectual Merits. Much progress has been accomplished recently in understanding the role of the structure on the physical properties of homogeneous elastomers composed of neutral flexible polymer chains. Carefully tailored syntheses, new analyses of physical measurements, and new computer simulation methods have been developed to study these polymer networks. It is now possible to address the more challenging task of understanding the properties of inhomogeneous elastomers. The presence of a discontinuous phase (made up of microdomains that either spontaneously form or are purposely introduced) is known or expected to dramatically affect the network mechanical properties. Two examples of such situations are polar domains formed in ionomers and densily-crosslinked domains formed in bimodal networks. Two types of inhomogeneous elastomers will be investigated by synthesizing model systems that will allow the identification of the molecular basis of the observed properties using NMR, X-ray, and neutron scattering measurements. Computer simulation of these systems will provide comparison with experimental results. Specific areas of research include: 1) the flow properties of precursor polysiloxane chains with interacting groups at regular intervals along their backbone; 2) the macroscopic and microscopic properties of endlinked networks synthesized from these precursor chains and the development of kinetic and equilibrium Monte Carlo simulations for comparison with experimental results; 3) the study of the properties of bimodal networks to test a recently proposed scaling that predicts the onset of short chain clustering that dramatically affect the properties of the elastomer. Broader Impacts. The particular materials to be investigated have potential applications in the area of conducting elastomers (in the case of ionomer networks), and in high-strength rubber fibers (in the case of bimodal networks). Scientific results will be disseminated through professional meetings and an industrial outreach program organized by Cornell Center for Material Research. Both graduate and undergraduate students will be working on the project; they will gain a good understanding of the synthesis and the chemical and physical properties of polymers and elastomers in particular. They will acquire a general appreciation for the coupling of experimental analysis and computer simulation that is becoming increasingly important for industry as the materials being engineered to benefit society become more complex.