Salt-Polymer Interaction in Concentrated Salt Dispersion XIAOHUA FANG Columbia University Center for Particulate & Surfactant Systems (CPaSS) IAB Meeting New York, NY August 20th, 2009

Possible Interactions in a Dispersion System Crystals of Salt Na+ CO32- H2O Step I: Figure out components in the system Ionic surfactant Nonionic surfactant Polymer backbones Electric Charges Na+ CO32- Salt/Surfactant Polymer/Surfactant Polymer/Salt Surfactant Mixture Step II: Understand 2-component systems Multi-component systems Step III: Understand 3-component systems

Introduction • Challenges in real formulations containing high salt concentration. – Homogenous or dispersed – Stable with time or temperature – Pourable in a wide range of temperature • The interaction of polyelectrolyte and salt Coil-Collapse-Re-expansion – Low salt concentration range à charge screened; polymer collapsed, etc. – Ultra-High salt concentration, morphology of polymer chain and its function?

Materials/Methods Materials *Sodium carbonate(Soda Ash) *Polyacrylic acid *Water * Other additives Methods *Salt-Polymer Interactions Density Light Scattering Conductivity Rheometry *Water related Interactions Water Activity

Radius of Gyration in concentrated salt solution Rg grows exponentially with salt level increase in entanglement Concentration

Hydrodynamic Radius in salt solution At higher salt level, PAA molecules oscillate within a larger effective region. RH increases with polymer concentration after a certain threshold PAA level.

Ion Condensation on Polymers Ion condensation happens and the salt species condensed onto PAA chains. Larger molecules are more effective in holding salts than smaller chains.

Speculation---Concentration Dependence Low Mw High Mw No Salt High Salt

Higher Salt Level More Rheological Sensitivity to PAA Concentration Viscosity increases with PAA concentration at all salt levels. At high salt level, the increase in viscosity with PAA concentration is more significant.

Higher Salt Level More Rheological Sensitivity to Temperature Viscosity decreases with temperature at all salt levels. At high salt level, the decrement in viscosity with temperature is more significant.

Schematic Diagram of Salt Ions Localization Small Molecule Temperature Large Molecule Low Temperature High Temperature

Concluding Remarks • As salt level increases, PAA 1. is unfolded and more hydrated. 2. plays a more dominant role on the rheological behavior of the system. 3. holds more salt locally. Larger molecules are more efficient in holding ions locally. •

Future Plans Conduct light scattering, rheological, conductivity measurements on multi-component system. 2. Elucidate the overall mechanism by which dispersion and flow properties are controlled in the system. We owe great thanks to: NSF-Industry/University Cooperative Research Center All the Industrial Collaborators