Investigation of the dynamic behavior of metallopolymers by combined experimental and theoretical methods

In this study, we investigate the structural changes in dynamic metallopolymers during stimulus application, i.e. thermal treatment. For this purpose, we focused on the synthesis of polymers containing terpyridine moieties as ligands in the side chains that were complexed with either iron(ii) or zinc(ii) salts. The resulting crosslinked metallopolymers were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and elemental analysis (EA). Rheology experiments, including dynamic mechanical thermal analysis (DMTA), frequency sweeps, stress relaxation and time-temperature superposition were conducted to study the stimuli-responsive mechanical properties. Hereby, the activation energy determined by stress relaxation as a combination of the metal complex and the polymer matrix could be determined. Additionally, computational master curves were obtained and the resulting relaxation spectra were analyzed. Beside the macroscopic material properties, temperature-dependent Raman spectroscopy and density functional theory (DFT) calculations were utilized to gain information on the changes on the molecular level. In this context, morphological changes in the polymer matrix were observed, which might be correlated to the presence of supramolecular aggregates. The changes on the molecular level could be linked to the macroscopic properties.