
260 Perturbation Theories for Fluids and Solids
The theory is readily extended to associating mixtures of spherical monomers
with dispersion interactions and multiple bonding sites. In this case, the free energy
takes the form (Chapman et al. 1988)
F
mix
Nk
B
T
=
F
(
0
)
mix
Nk
B
T
+
F
bond
mix
Nk
B
T
+
F
MF
mix
Nk
B
T
, (8.149)
where F
bond
mix
is given by Equation 8.89 and the van der Waals MF contribution by
F
MF
mix
Nk
B
T
=−
ρ
k
B
T
m
i=1
m
j=1
x
i
x
j
a
ij
, (8.150)
where m is the number of components in the mixture. Now, the SAFT expression
for the EOS in the case of monomers with a HS core and one or two bonding sites
is obtained by adding to Equation 8.92 the MF contribution, in a similar