Enthalpies of vaporization of oligomers of poly(hexamethylene sebacate) and esters of alkylcarboxylic acids

Abstract

Enthalpies of vaporization for esters covering a molecular weight range of about 74–939 g/mol · [monocarboxylics; linear esters of sebacic series; branched esters of triglyceride series; and, oligomer esters of poly(hexamethylene sebacate)] and a temperature range of about 273.15–523.15 K have been empirically fitted to within about 5% to an equation of the following form: ΔHv(T,M) = S(T)f(M) + I0(T), where S(T) = C Ln(T) + K0, I0(T) = aT + b0, and f(M) = M/(1 + a0M), M is the molecular weight (molar mass); T is in degrees Kelvin; and, C, K0, a, b0, and a0 are constants. These results were used to determine the heat capacity difference, ΔCp = Cp(l) − Cp(g), and compared to calculated values from functional relationships of Cp(l) and Cp(g), l is liquid g is gas. The heat capacity difference results in conjunction with Cp(l) were used to empirically calculate the heat capacity of the gas, Cp(g), over the molecular weight and temperature ranges investigated and compared to a group contribution method. The functional forms for ΔHv(T,M), ΔCp(T,M), Cp(l), and Cp(g) were also found to be applicable for n-alkanes. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 731–746, 1998