Binding interaction between 1-octyl-3-methylimidazolium bromide and sodium polystyrene sulfonate in aqueous solution

Abstract

Binding interactions between surface active ionic liquid (SAIL) [C8mim][Br] and sodium polystyrene sulfonate (NaPSS), an anionic polyelectrolyte were analyzed from techniques such as conductometry, tensiometry, dynamic light scattering (DLS) and fluorimetry. Typical surface tension profile shows the existence of noticeable elevation in the value of surface tension at IL concentrations before the critical micelle concentration (cmc) of the SAIL. By using conductivity measurements we have calculated the cmc and degree of ionization, α, at various temperatures from 298.15 to 318.15 K. A series of thermodynamic parameters like standard enthalpy of micellization (ΔHm°), standard free energy of micellization (ΔGm°) and standard entropy of micellization (ΔSm°) have been evaluated. Behavior of fluorescence probe, pyrene and DLS measurements confirm the binding interactions between SAIL and the polyelectrolyte. It has been found that the cmc values significantly increase with higher concentration of polyelectrolyte due to hydrophobic interactions. The Gibb's free energy (ΔGm°) is negative for the above systems and increases with increasing polyelectrolyte concentration.