Cooperative and molecular dynamics of alcohol/water mixtures: the view of dielectric spectroscopy

The excess activation free energy, ΔGE, enthalpy, ΔHE, and entropy, ΔSE, of the cooperative relaxation time, τ1, and their partial molar quantities, ΔGiE, ΔHiE, and ΔSiE (i=alcohol, A, or water, W) are discussed. Above the boundary concentration Xb (MW: Xb∼0.30; EW: 0.18; 1PW: 0.14; 2PW: 0.15), ΔHAE and ΔSAE remain nearly zero, indicating that alcohol molecules in the mixtures already form a zigzag chain structure similar to pure liquids but branched by inserted water molecules. The two pertinent maxima of ΔHAE and ΔSAE in the water-rich region at X1 and X2 (MW: X1∼0.045; EW: 0.04; 1PW: 0.03; 2PW: 0.03; MW: X2∼0.12; EW: 0.08, 1PW: 0.06; 2PW: 0.07) are connected with the hydrophobic hydration of alcohol monomers (X1) and small multimers (X2) predominating at these concentrations.