Thermodynamics of n‐alkane systems and the solution theories of flory and prigogine

Abstract

synopsisThe partial molar excess free enthalpies and enthalpies as well as the molar excess enthalpies of a number of n-alkane systems were reexamined within the scope of the polymer solution theory of Flory, Orwoll, and Vrij and that of Prigogine in the version after Delmas, Patterson, and Somcynsky. A semiempirical method was used to obtain characteristic n-alkane data, which obey the principle of corresponding states. By using these data (instead of those from the partition function after Flory and collaborators), a physically realistic interpretation of the excess free enthalpies over the whole concentration range is possible if the combinatorial contribution is purely athermal in nature. Both theories give an enthalpy interaction parameter near zero as expected, whereas neither a significant end effect nor an entropic interaction contribution is apparent from the analyses of the excess free enthalpies. The poor results obtained for the partial excess enthalpies and the enthalpies of mixing reflect the inadequacy of the partition functions on which these modern solution theories are based.

The significance of the exponent n in the energy-volume relation, E=-A/Vn, in the behavior of fluids and fluid mixtures.

“…The energy of a binary solution is given by -E =(An7]n+A2iY]22+Aur]n)lvn (13) where All9 A22, and A12 are the number of contact Eq. ( 13) can be rewritten to read -E=(s1r1Nl7]11+s2r2N2y]^-A^Ar])l2^n (15) where Ar]=r]11-\-rj22-2rjl2 and Sir^and s2r2N2 represent the total number of contact sites of kind 1 and 2, respectively.…”