US-Egypt Cooperative Research: Segmental Orientation and Strain Induced Crystallization in Regular Bimodal Poly (tetramethylene oxide) (PTMO) Elastomers

描述：该奖项是为了表彰辛辛那提大学化学系的James E.Mark博士和Gregory Beucage博士以及埃及开罗大学贝尼-苏伊夫分校化学系的M.A.Sharaf博士的合作项目。本研究的主要目的是研究影响弹性体重要力学性能的因素。这些科学家计划使用官能化的聚四亚甲基氧化物(PTMO)低聚物，通过受控的末端连接反应，制备由非常短的链和相对长的链混合而成的规则的双峰网络。在这样的网络中，通过使每个连接连接到固定数量的长链和短链来确保规律性。最终性质的改善是由于与短链的有限延伸性有关的固有的分子内效应。此外，这些特殊的网络很容易受到应变诱导结晶的影响，结晶增强会显著改善最终性能。这样制备的网络将被用来更好地理解橡胶弹性、链段取向和应变诱导结晶的相关分子方面。范围：将散射技术的数据与模数、双折射和红外二向色性测量相结合，为分析短链和长链的复杂结构特征的尺寸尺度与一般物理性质之间的相互作用提供了强大的工具。此外，还将使用机械性能和散射技术来研究这些具有良好特性的弹性网络中应变诱导结晶的热力学和动力学方面。这些研究可以通过分子设计获得具有优化结构-性能关系的弹性体。这次合作为两国与会者带来了独特的兴趣和研究经验，以改善和优化这种具有重要经济意义的弹性材料的性能。该奖项还将使一名美国初级科学家和一名美国研究生获得国际研究经验。该项目完全符合国际方案司的目标。

Description: This award is for support of a cooperative project by Dr. James E. Mark and Dr. Gregory Beaucage of the Department of Chemistry at the University of Cincinnati and Dr. M.A. Sharaf, Department of Chemistry, Cairo University at Beni-Suef, Egypt. The main objective of this research is to study factors that influence the important mechanical properties of elastomers. These scientists plan to use functionally capped poly(tetramethylene oxide) (PTMO) oligomers to prepare regular bimodal networks of a mixture of very short chains with relatively long chains, through controlled end linking reactions. In such networks, regularity is ensured by having each junction connected to a constant number of both long and short chains. Improvements in the ultimate properties are due to innate intramolecular effects pertaining to the limited extensibility of short chains. In addition, these particular networks are susceptible to strain-induced crystallization with remarkable consequent improvements in ultimate properties from crystalline reinforcement. The networks so prepared will be employed to better understand the relevant molecular aspects of rubber elasticity, segmental orientation, and strain-induced crystallization. Scope: The combination of data from scattering techniques with those of the modulus, birefringence, and infrared dichroism measurements provides a powerful tool for analysis of the interaction between the size-scale of the complex structural features of both short and the long chains and physical properties in general. Also, mechanical properties and scattering techniques will be employed to investigate both the thermodynamic and kinetic aspects of strain-induced crystallization in these well-characterized elastomeric networks. These studies can result in obtaining elastomers with optimized structure-property relationships through molecular design. The collaboration brings a unique combination of interest and research experiences of the participants from the two countries for improving and optimizing the properties of the economically-important elastomeric materials. This award will also enable a junior US scientist, and a US graduate student, to gain international research experience. The project is well in line with the objectives of the Division of International Programs.