Structure and Dynamics of a Bisurea-Based Supramolecular Polymer in n-Dodecane.
June 29th, 2008 | by admin |Structure and Dynamics of a Bisurea-Based Supramolecular Polymer in n-Dodecane.
The structure and dynamics of a supramolecular polymer formed by a bisurea-type compound, 2,4-bis(2-ethylhexylureido)toluene (EHUT), in an apolar solvent, n-dodecane (C 12), were examined in detail. The EHUT/C 12 organo-gel system forms long, dynamic chain-like supramolecular polymers, which lead to an entangled network showing remarkable viscoelastic behavior with two major relaxation modes. A slow relaxation mode with an approximately constant relaxation time, tau S, was observed in a flow region and the other, fast, relaxation mode with a time tau F1 (<tau S) was observed in a high-frequency range. Because no dielectric relaxation behavior was observed over a frequency region including the mechanical tau S and tau F1 relaxation modes, the formed supramolecular polymer does not possess any total dipole moment due to antiparallel intermolecular hydrogen bonding of the two ureido groups of each EHUT unit. A structural model for the supramolecular polymer formed in EHUT/C 12 is proposed based on force-field simulations. This proposed model is consistent with all the experimental data concerning this system: flow birefringence measurements, dielectric spectroscopy, SANS, and FTIR.
Shikata T, Nishida T, Isare B, Linares M, Lazzaroni R, Bouteiller L.
Department of Macromolecular Science, Osaka University, Toyonaka, Osaka 560-0043, Japan, Laboratoire de Chime des PolymeÌ€res, UMR 7610, UniversiteÌ Pierre et Marie Curie-CNRS, 4 place Jussieu, 75252 Paris Cedex 05, France, and Service de Chimie des MateÌriaux Nouveaux, UniversiteÌ de Mons-Hainaut/Materia Nova, Place du Parc, 20, B-7000 Mons, Belgium shikata@chem.sci.osaka-u.ac.jp.