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

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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.