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: Δ Hv ( T,M ) = S ( T ) f ( M ) + I 0 ( T ), where S ( T ) = C Ln( T ) + K 0 , I 0 ( T ) = aT + b 0 , and f ( M ) = M /(1 + a 0 M ), M is the molecular weight (molar mass); T is in degrees Kelvin; and, C, K 0 , a, b 0 , and a 0 are constants. These results were used to determine the heat capacity difference, Δ C p = C p ( l ) − C p ( g ), and compared to calculated values from functional relationships of C p ( l ) and C p ( g ), l is liquid g is gas. The heat capacity difference results in conjunction with C p ( l ) were used to empirically calculate the heat capacity of the gas, C p ( g ), over the molecular weight and temperature ranges investigated and compared to a group contribution method. The functional forms for Δ Hv ( T,M ), Δ C p ( T,M ), C p ( l ), and C p ( g ) were also found to be applicable for n ‐alkanes. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 731–746, 1998