The Response of Polyelectrolytes to Shear - Studies by Single Molecular Fluorescence Spectroscopy

To understand the molecular mechanism of the unique rheological properties of polyelectrolyte solutions, in-situ investigations into the counterion distribution and the effective charges of the main chain have been conducted by single molecule fluorescence spectroscopy.  By examining the local concentration of the hydronium ions around the model polyelectrolyte, sodium polystyrene sulfonate (NaPSS), the investigations have discovered that the counterions depart from the charged main chain, showing that the effective charges of the chain increases by shear. Systematic studies have been performed under different conditions, including molecular weight, salt concentration and polyelectrolyte concentration, by both steady and oscillatory shear. The information has demonstrated the microscopic picture of polyelectrolyte solution under shear - the alternation of the dynamic network formed inside the solution due to the long-range electrostatic inter-chain repulsion.