COLL 404 |
| Jasper van der Gucht1, Wout Knoben1, Nicolaas A. M Besseling1, Gerard Fleer1, Laurent Bouteiller2, and Martinus A Cohen Stuart3. (1) Laboratory of Physical Chemistry and Colloid Science, Wageningen University, PO box 8038, 6700 EK Wageningen, Netherlands, (2) Departement of polymer chemistry, Université Pierre et Marie Curie, 4, Place Jussieu, Tour 44-54, 1er étage, 75252 Paris, France, (3) Physical Chemistry & Colloid Science, Wageningen University, PO Box 8038, 6700 EK Wageningen, Netherlands |
| We have studied solutions of bis(ethylhexylureido)toluene (EHUT) in alkane solvents where this substance self-assembles into supramolecular polymers which are relatively rigid. From light scattering, we obtained the correlation length, and from various rheological measurements the low shear viscosity, the storage and loss moduli, all as a function of EHUT concentration in the semidilute regime. Colloidal silica particles of 250 nm, dispersed in these solutions, have a strongly modified diffusion behaviour which clearly shows both the structure and the dynamics of the EHUT solution. The autocorrelation function has two 'waves' indicating both a short-time and a long-time diffusive mode, separated by a transition region due to trapping in the EHUT transient network. The long-time diffusion could be correlated with the rheological data. EHUT solutions at concentrations of a few percent also show very pronounced non-linear rheological effects at shear rates as low as 0.01 s-1, and in rheo-optical measurements, clear shear-banding behavior was observed. Possible explanations are discussed. |
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“Smart” Polymers on Surfaces and Colloids
8:30 AM-11:40 AM, Wednesday, March 31, 2004 Marriott -- Grand Ballroom J, Oral
Division of Colloid and Surface Chemistry |