Microcalorimetric Studies Of The Interaction Enthalpies Of Some Complicated Fluids

In this thesis,the interaction enthalpies in microemulsions,(OmimBF4+alcohol)mixtures and glycine betaine aqueous solutions have been investigated by microcalorimetry.The studies include the following contents.1.The dilution enthalpies of the microemulsion droplets were determined by isothermal titration microcalorimetry(ITC)and used to explore the interaction enthalpies-?Hc between the droplets for the system of AOT/H2O/n-alkane with different water contents ?(=[H2O]/[AOT])and chain lengths n of n-alkane.It was fond that-?Hc increased monotonically with ?,and changed from the negative to the positive at ??10,while it remained unchanged for?>20.The values of-?Hc have the minimum at n = 10 for ? = 5 and the maximum at n = 10 for ? =15.The results of ITC are also verified by flow-mixing calorimetry.The effects of RW and n on-?Hc were discussed by the contributions of the overlapping of the surfactant tails between two neighboring droplets and the releasing of the entrapped solvent molecules.2.Effects of various kinds of additives,which included a number of polymers,salts and small organic molecules,on the interaction enthalpies-?Hc between the droplets of AOT/H2O/oil microemulsions were determined by ITC.The effects of the additions with different molecular weights,concentrations and structures on-AHc were discussed by the location of the additives in microemulsions and the electrostatic interactions,hydrogen bonds and hydrophobic interactions between the additives and AOT.3.The interaction enthalpies-?Hc between the droplets of(AOT + other surfactant)/H2O/n-hepane mixed reversed microemulsions with co being 5 and 15 respectively were determined.The effects of the structures and the contents of the other surfactants on-?Hc were discussed by the packing parameters of the mixed surfactants,the hydrophilicity,the hydrophobicity and the electrostaticity of the surfactant molecules.4.The interaction enthalpies-?Hc between the droplets of BmimBF4/TX-100/cyclohexane microemulsions with different molar ratios(Rs)of BmimBF4 to TX-100 were determined by ITC.The interaction enthalpies between droplets were attractive and their absolute values increased with Rs,which were interpreted by the structural difference between TX-100 and cyclohexane and the structural change of droplets with Rs.5.An isothermal titration calorimeter was used to measure the excess molar enthalpies HE for mixtures of OmimBF4 and various alcohols,which were all positive.The magnitude order of HE was explained by the balance between the enthalpies of the alcohol/alcohol and the alcohol/OmimBF4 interactions.The enthalpies of dilution were measured for glycine betaine in water and aqueous solutions of NaCl or KCl using a flow-mixing microcalorimeter.The enthalpic interaction coefficients h2 and h3 were determined.It was found that the enthalpic pairwise interaction coefficients h2 of glycine betaine in both brine solutions were positive and increased with the molality of the salts,and h2(NaCl)>h2(KCl)at the same molality.It was attributed to the partly remove of the water molecules and the cations from the hydration layer when two GB molecules closed up.