High-Temperature Transitions in Metallopolymers Crosslinked With 2,6-bis(1'-methylbenzimidazolyl)pyridine Metal-Ligand Complex

Report No. ARL-TR-6706
Authors: Aaron C. Jackson; Robert H. Lambeth; Victor Rodriguez-Santiago; Brady G. Butler; Frederick L. Beyer
Date/Pages: October 2013; 26 pages
Abstract: Metallopolymers have reversible bonding properties and strong phase separation behavior that make them useful for a variety of applications. However, relaxation processes within the polymer, specifically relaxation processes within the metal-ligand (ML) rich phase, are not fully understood. This report proposes that scission of the ML bond and softening of the ML-rich phase within the polymer are the primary relaxation processes occurring above room temperature. Dynamic mechanical analysis (DMA) tests show that both play a role in the degradation of the mechanical properties above 100 °C. In polymers containing cobalt and iron, the two relaxation processes were separate while these relaxation processes were interdependent in polymers containing copper and zinc. Under static conditions, no relaxation processes were evident as measured by ultraviolet/visible (UV/Vis) light spectroscopy, small-angle x-ray scattering (SAXS), and x-ray diffraction (XRD). These results highlight the importance of the ligand chemistry and counter ion, two components of metallopolymers that may have a large impact on the softening point of the ML-rich phase. They also highlight a need to study changes in the morphology and spectral response of metallopolymer under mechanical stress.
Distribution: Approved for public release
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Last Update / Reviewed: October 1, 2013