Computer Simulations of Self-Assembly of Metallo-Supramolecular Networks – Elena Dormidontova

Date: Sat. October 31st, 2009, 12:30 pm-1:30 pm
Location: Rockefeller 221

Using Monte Carlo simulations we studied formation of reversible metallo-supramolecular networks based on 3:1 ligand-metal complexes between end-functionalized oligomers and metal ions. The fraction of 1:1, 2:1 and 3:1 ligand-metal complexes in reversibly associated structures was analyzed as a function of oligomer concentration, c and metal-to-oligomer ratio. We studied the onset of network formation, which occurs in a limited range of metal-to-oligomer ratios at sufficiently large oligomer concentrations as well as the properties of metallo-supramolecular networks. We found that the mesh size of the network decreases with oligomer concentration and reaches its minimum at the stoichiometric composition, where the high-frequency elastic plateau modulus approaches its maximal value. At high oligomer concentrations the elastic plateau modulus follows a c^1.8 concentration dependence, similar to recent experimental results for metallo-supramolecular networks. We have also studied the special case of cis- trans-switchable 2:1 ligand-metal complexes and investigated the influence of isomerisation on the formation and properties of metallo-supramolecular networks. We found that that the sol-to-network transition can be induced by trans-cis isomerization in a large range of oligomer number densities and metal-to-oligomer ratios. The cis-trans isomerization also significantly influences the elastic properties of the metallo-supramolecular network such as elastic plateau modulus or mesh size. These switchable properties of metallo-supramolecular networks suggest interesting application opportunities.