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Shear-induced structure in polymer-clay nanocomposite solutions
S Lin-Gibson1, H Kim, G Schmidt
1Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8543, USA.
Journal of Colloid and Interface Science
|May 18, 2004
Summary
Polymer-clay nanocomposite gels form physical gels. Shear flow disrupts this network, causing phase separation and unique clay platelet orientation, unlike other nanocomposites.
Area of Science:
- Materials Science
- Polymer Science
- Colloid Science
Background:
- Polymer-clay nanocomposites form physical gels through polymer bridging and reversible adsorption.
- Understanding the shear response of these dynamic networks is crucial for material design.
Purpose of the Study:
- To investigate the equilibrium structure and shear response of model polymer-clay nanocomposite gels.
- To elucidate the relationship between shear flow, network disruption, and emergent structures.
Main Methods:
- X-ray scattering
- Light scattering
- Optical microscopy
- Rheometry
Main Results:
- Shear flow induces macroscopic domain patterns due to coupled composition and stress.
- Clay platelets orient with their surface normal parallel to the vorticity direction.
- No stress plateau was observed during shear-induced phase separation, differing from flow-induced banding.
Conclusions:
- Macroscopic phase separation under shear flow leads to distinct structural and orientational behaviors in polymer-clay nanocomposite gels.
- The observed platelet orientation differs from polymer-melt systems due to shear-induced phase separation effects.