Measurement and Prediction of the Molar Heat Capacities of Liquid Polyoxyethylene Glycol Monoalkyl Ethers (CnEm)

The saturation heat capacities of eleven polyoxyethylene glycol monoalkyl ethers (CnEm) were measured by the calorimetric (DSC) method. The measurements were performed within the temperature range of (275.15 to 339.15) K by means of Micro DSCIII (Setaram) calorimeter. Assuming that the molar heat capacity (C-p,C-m) shows an additive character, the contributions to the C-p,C-m values of particular functional groups forming the compounds of CnEm series were calculated. Two models differing in the manner of molecule division into functional groups, i.e., first- and second-order additivity group contribution approach, were used. In the latter, not only the type of functional group but also its position and the closest neighborhood was taken into account. The average deviations between the experimental values of Cp and those estimated on the basis of the group contributions do not exceed 0.4 % for the compound of the series under investigation. The group contributions determined in this study make it possible to predict the molar heat capacity of monoethers CnEm within the temperature range of (270 to 350) K with an average error below 1 %.