Design, Characterization, and Evaluation of Elastomeric Materials

9422223将使用官能化聚合物链的标记末端连接来获得已知结构和受控结构的弹性体。其中一些将包含悬链不规则性，另一些将包含网络链长的单峰和多峰分布。将包括三峰网络和异常广泛的伪单峰网络，这些网络是通过将单独制备的分子量变化很大的一批聚硅氧烷组合在一起而获得的。在具有其他方面不寻常的结构的条件下，例如通过在溶液中或在应变状态下进行交联会产生额外的弹性体。将进行实验，以识别拉伸、双向拉伸、剪切和扭转中的应变诱导结晶。还将进行模拟，以表征在一些新的具有异常高立体规整性的聚硅氧烷链中发生的结晶。还将研究弹性凝胶，包括一些涉及提供增强取向液晶聚合物的加工技术的研究。将研究凝胶化动力学，以及溶剂进入和离开膨胀网络的扩散系数。新型增强填料将通过有机金属材料如硅酸盐、钛酸盐、锆酸盐、铝酸盐和简单金属盐如三氯化铁的水解、光解或热解来制备。特别重要的是确定使增强效果最大化的颗粒尺寸，并表征颗粒形状的影响。最终得到的填充增强弹性体将主要通过机械性能测量、电子微孔以及X射线和中子散射来表征。此外，还将进行模拟，以阐明填充增强弹性体的增强机理。最后，对陶瓷为连续相的聚合物-陶瓷混杂复合材料的抗冲击性能进行了实验研究。%这些项目的主要意义在于更好地从分子上了解橡胶类弹性以及填充剂增强弹性体的方式。研究结果将为生产具有特殊机械性能的弹性体材料和弹性体改性陶瓷提供重要的指导。

9422223 Mark End linking of functionally-terminated polymer chains will be used to obtain elastomers of known and controlled structures. Some will contain dangling-chain irregularities, and others unimodal and multimodal distributions of network chain-lengths. Included will be trimodal networks and unusually broad pseudo-unimodal networks obtained by combining separately-prepared batches of polysiloxanes of widely varying molecular weights. Additional elastomers will be produced under conditions giviing structures that are unusual in other respects, for example by cross linking in solution or in a state of strain. Experiments will be performed for identifying strain-induced crystallization, in elongation, biaxial extension, shear, and torsion. Simulations will also be carried out to characterize the crystallization occurring in some new polysiloxane chains of unusually high stereoregularity. Elastomeric gels will also be studied, including some involved in processing techniques giving liquid-crystalline polymers of enhanced orientation. Gelation kinetics will be studied, as will diffusion coefficients of solvents into and out of swollen networks. Novel reinforcing fillers will be prepared by the hydrolysis, photolysis, or thermolysis of organometallic materials such as silicates, titanates, zirconates, aluminates, and simple metal salts such as ferric chloride. Of particular importance will be identifying the particle size that maximizes reinforcement, and characterizing the effects of particle shape. The resulting filler-reinforced elastomers will be characterized primarily by mechanical property measurements, electron microsocpy, and by X-ray and neutron scattering. Simulations will also be carried to elucidate reinforcing mechanisms in filler-reinforced elastomers in general. Finally, experiments will be carried out to exploit the ability of elastomeric domains to improve the impact resistance of polymer-ceramic hybrid composites in which the cer amic is the continuous phase. %%% The primary significance of these projects is the achievement of a better molecular understanding of rubberlike elasticity and the ways in which fillers reinforce elastomers. The results should provide importance guidance for producing elastomeric materials and elastomeric- modified ceramics having unusaully attractive mechanical properties.