Thermodynamics of the binding of TNS and auramine O by isotactic PHEMA in aqueous solution

Abstract

The binding of 6-p-touidine-2-naphthalene sulfonate and auramine O to isotactice-poly (2-hydroxyethyl methacrylate) was studied to obtain information on the nature of the interaction between the PHEMA and the dye by equilibrium dialysis, fluorometry and viscometry in the range of 5 - 35℃. The first binding constant and the thermodynamic parameter in the equilibrium dialysis experiments have been calculated. It was found that the free energy change is negative and the enthalpy and the entropy change are largely positive. The results obtained above show that hydrophobic interaction is predominant in the binding of auramine O and TNS by isotactic PHEMA. Temperature dependence of fluorescence intensity (dI/dT) of auramine O in the various salts solution of isotactic PHEMA are also investigated. In the water structure-breaking salt solutions of isotactic PHEMA, Temperature dependence of the fluorescence intensity of auramine O dI/dT is decreased as the ionic B coefficient is decreased. These results can be interpreted in terms of the concept that water structure-breaking salt reduces the structure of the aqueous environment and hence lowers the formation of hydrophobic interactions.