The physicochemistry of interaction of the ionic liquid (IL), 1-butyl-3-methylimidazolium octylsufate (C4mim) (C8OSO3) with the anionic polymer sodium polystyrene sulfonate, (NaPSS) has been studied using tensiometry, conductometry and fluorimetry. The critical aggregation concentration (cac), the standard Gibb’s free energy, the standard enthalpy change, and standard entropy change, upon aggregation for the IL in solutions have been derived from the conductance data. Further to get the deeper insights into the aggregation process spectroscopic study using fluorescence measurements have been carried out. The aggregation behaviour observed from conductance, surface tension and fluorescence probe has been found to be in good agreement with each other. Behaviour of fluorescence probe confirms the binding interactions between IL and the polyelectrolyt
