In this project, funded by the Macromolecular, Supramolecular, and Nanochemistry Program of the Chemistry Division, Kenneth Wagener and Stephen Miller of the Department of Chemistry at the University of Florida will investigate the architectural expansion of available polyolefin structures. This objective will be made possible through a variety of methods. With newly developed single-site catalysts, characteristics such as catalyst structure, activation processes, polymerization kinetics-under homogeneous as well as heterogeneous conditions-and, especially, immobilization/supporting techniques will be controlled for the development of new polymerization systems. Key parameters include control of tacticity, product morphology (size, shape of product particles), polymer molecular weight, comonomer incorporation, and comonomer sequence distribution. Special challenges to be addressed are the formation of core-shell structures of polyolefins and the use of polar monomers. Also, the elusive formation of polyolefin nanoparticles will be sought. An interdisciplinary approach will be applied and strengths found in five separate research groups will be combined and exploited. The five lead investigators are Klaus Müllen (Max-Planck Institute for Polymer Research, Mainz, Germany), Brigitte Voit (Leibniz-Institute für Polymerforschung, Dresden, Germany), Kenneth Wagener, Stephen Miller, and Heloise O. Pastore (Universidade de Campinas, Brazil). The broader impacts involve holding workshops on the research topics, scientific interactions with polyolefin companies, and international training of U.S. graduate students. Graduate students will conduct their research projects in the laboratory of a foreign collaborator for several months. These student exchanges will help develop an infrastructure for research and education and greatly enhance the international dimension of their training experience.
The successful execution of this research project will result in new plastic materials with properties that are improved and finely-tuned compared to available products. There exists a wide variety of potential applications, including strong lightweight plastics, composite materials, and specialty polymers.
Abstract: Structural characterizations such as: Wide-angle X-ray scattering (WAXS) and temperature-dependent FTIR spectroscopy were used to understand hydrogen bonding interactions of a hydroxy functional polyethylene prepared by Acyclic Diene Metathesis (ADMET) polymerization. The polymer under investigation contained an OH branch precisely placed on every 21st carbon, a representative of a large class of precision polyalcohols. It displays an orthorhombic unit cell structure with characteristic reflection planes at (110) and (200), equivalent to pure crystalline polyethylene (PE). These data unambiguously validate that the OH functional group is excluded from the PE crystalline domain. Furthermore, the polymer melts 100 oC higher than all previous similar polymers possessing precision placed long alkyl branches that also are excluded from PE lamellae. Temperature-dependent FTIR spectroscopy from room temperature to 150 oC, followed by cooling to 125 oC supports exclusion of the hydroxyl group from the unit cell. We conclude that these hydroxyl groups form stable physical networks in the amorphous region via hydrogen bonding and are essential for the overall morphology of such polymers.
