College Park, Maryland June 6 - 10 , 2004 |
MP6: Orientation and Relaxation of Polymer-Clay Solutions
M. Malwitz (Louisiana State University), P. Butler (Oak Ridge National Laboratory), L. Porcar (National Institute of Standards and Technology), G. Schmidt (Louisiana State University)
The influence of shear on viscoelastic poly(ethylene)oxide (PEO)-clay solutions (Montmorillonite, CNA) was investigated by means of rheology and small-angle neutron scattering (SANS). Steady state viscosity and SANS were used to measure the shear-induced orientation and relaxation of polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates and the CNA clay platelets aligned by the flow, with the surface normal parallel to the gradient direction. Cessation of shear lead to partial and slow randomization of CNA platelets while extremely fast relaxation was observed for Laponite (LRD) platelets. This work on PEO-CNA network like solutions is compared to previously reported PEO-LRD networks and focuses on differences and similarities in shear orientation, relaxation, and on the polymer and the clay interactions.
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