Influence of metal ion and polymer core on the melt rheology of metallosupramolecular films

Figure Persented: Detailed rheological studies of metallosupramolecular polymer films in the melt were performed to elucidate the influence of the metal ion and polymer components on their mechanical and structural properties. 4-Oxy-2,6-bis(N-methylbenzimidazolyl)pyridine telechelic end-capped polymers with a low-T _g core, either poly(tetrahydrofuran) or poly(ethylene-co-butylene), were prepared with differing ratios of Zn ²⁺ and Eu ³⁺ to determine the influence of polymer chain chemistry and metal ion on the properties. Increasing the amount of the weaker binding europium yielded more thermoresponsive films in both systems, and results show that the nature of the polymer core dramatically affected the films mechanical properties. All of the films studied exhibited large relaxation times, and we use this to explain the pure sinusoidal behavior found in the "nonlinear" viscoelastic region. Basically, the system cannot relax during a strain cycle, allowing us to assume the network destruction and creation rates to be only a function of the strain amplitude in a simplified network model used to rationalize the observed behavior.