Syntheses, Structures, Properties, and Applications of Some Novel Elastomers

该计划的基本目标是获得可用于优化弹性体材料性能的结构-性能关系。例如，各种弹性材料在拉伸、双向拉伸、剪切和扭转方面的应力-应变结果将使用基于纠缠约束网络连接的分析理论和计算机模拟来解释。弹性体既包括通过行业中使用的一些相对不受控制的技术进行交联的具有商业重要性的聚合物，也包括一些使用更具选择性的反应制备的弹性体，这些反应旨在提供更好的已知结构网络结构。这种量身定制的网络将通过末端连接官能化端基聚合物链来制备，这种方法也可以用于合成具有多峰网络链长分布的不寻常网络。这些结果应该会更好地从分子上理解橡胶状弹性，并为设计具有异常吸引人的机械性能的材料提供指导。对这些材料特别感兴趣的实验将是确定最大延伸率和韧性的应力-应变测量。新型的增强填充剂，如二氧化硅，将通过有机硅酸盐等前体和简单金属盐(如三氯化铁)的水解原位生成。特别重要的是确定最大化增强的颗粒大小，并表征最大化增强的颗粒大小的影响，以及表征颗粒形状和非球形颗粒的取向的影响。通过将一种类型的颗粒与另一种类型的陶瓷包覆来制备新型材料。还可以通过增强沸石来制备螺纹状弹性体链，并制备可以通过磁场操纵的填充物。最终得到的填充增强弹性体将主要通过机械性能测量、电子显微镜以及X射线和中子散射进行表征。两种较新的方法已经显示出相当大的前景，它们是脉冲传播测量和布里渊光谱分析。这个项目专注于学习如何控制弹性材料的结构，以使其机械性能最大化。最重要的结构特征是弹性体的化学性质以及它们如何连接到网络中，最重要的特性是它们的强度、延伸性和韧性。所采取的方法主要是实验性的，但将以并行计算机模拟和分析理论为指导。

The basic goal of this program is to obtain structure-property relationships that can be used to optimize the properties of elastomeric materials. For example, stress-strain results on a variety of elastomeric materials in elongation, biaxial extension, shear, and torsion will be interpreted using both analytical theories based on entanglement-constrained network junctions, and computer simulations. Elastomers will include both commercially important polymers cross linked by some of the relatively uncontrolled techniques used in the industry, but also some elastomers prepared using more selective reactions designed to give networks of better known structure. Such tailor-made networks will be prepared by end linking functionally-terminated polymer chains, an approach that can also be used to synthesize unusual networks with multimodal network chain-length distributions. These results should give a much better molecular understanding of rubberlike elasticity, and provide guidance in the design of materials of unusually attractive mechanical properties. Experiments on these materials that are of particular interest will be stress-strain measurements for identifying maximum extensibilities and toughness. Novel reinforcing fillers such as silica will be generated in-situ by hydrolyses of precursors such as organosilicates, and simple metal salts such as ferric chloride. Of particular importance will be identifying the particle size that maximized reinforcement, and characterizing the effects of particle size that maximizes reinforcement, and characterizing the effects of particle shape and the orientations of non-spherical particles. Novel materials will be prepared by coating particles of one type with a ceramic of another type. It will also be possible to the thread elastomeric chains through reinforcing zeolites, and to prepare fillers that can be manipulated by a magnetic field. The resulting filler-reinforced elastomers will be characterized primarily by mechanical property measurements, electron microscopy, and by X-ray and neutron scattering. Two newer approaches which already show considerable promise are pulse-propagation measurements and Brillouin spectroscopy.This project is focused on learning how the structures of elastomeric materials can be controlled in order to maximize their mechanical properties. The most important structural features are the chemical natures of the elastomers and how they are linked into networks, and the most important properties are their strengths, extensibilities, and toughness. The approaches taken are primarily experimental, but will be guided by parallel computer simulations and analytical theory.