Excess molar enthalpies of binary mixtures containing glycols or (polyethylene) glycols+propylene carbonate at 308.15 K

Excess molar enthalpies, HmE, were determined as a function of molar fraction at 308.15 K and at atmospheric pressure for the binary mixtures containing propylene carbonate with ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, poly(ethylene glycol)-200, poly(ethylene glycol)-300, poly(ethylene glycol)-400, and poly(ethylene glycol)-600. Values of HmE range from a maximum of about 1640 J mol−1 (propylene glycol) to a minimum of about −386 J mol−1 (PEG-600). All mixtures containing monodisperse glycols have positive values of HmE. Also PEG-200 presents a curve of HmE versus x1 (the molar fraction of glycol, component 1) always positive, whereas PEG-600 presents negative values of the heat of mixing over the whole range of the molar fraction. Finally, PEG-300 and PEG-400 show an inversion of sign of HmE, at about x1=0.7 and 0.3, respectively. The experimental data were correlated using the Redlich–Kister polynomial and the adjustable parameters were obtained by the least-squares method. A qualitative discussion have been made in terms of intermolecular H-bonds.