Structure and dynamics relationships in coordinatively cross-linked polymer networks

CHED 447

Bethany M. Neilson, bmn3@duke.edu, Sung Lan Jeon, ippsljeon@hotmail.com, David M. Loveless, dml8@duke.edu, and Stephen Craig, stephen.craig@duke.edu. Department of Chemistry, Duke University, Box 90346, Durham, NC 27708
Reported here is a study of reversibly associative polymer networks defined by metal-ligand coordination of bimetallic Pd(II) pincer cross-linkers with poly(4-vinylpyridine) in DMSO. The mechanical properties, including the viscosity and elasticity, of the networks formed depend on the ligand exchange kinetics of the metal-ligand coordination complex, which are dictated by the choice of metal complex. Oscillatory rheology was used to measure the viscosity and elasticity of the gels formed by the networks. At sufficiently high concentration of the cross-linker, the network mechanical properties are independent of the cross-linker structure that links the two metal sites. At concentrations near the percolation threshold, however, differences between cross-linker structures are observed.