potential with a temperature dependent segment diameter, dl, given by
/ ^repulsion
dr = σi 1 — 0.12 exp
(2.5)
1 - exp I —-———
p ∖ kT
Thus, the excess contribution to the free energy due to repulsive interactions is given
by [82, 83]
Ahs
NsKT
ɪ Γ ɜɑɑ
Co . 1 - Сз
C3
<3 (I - Сз)2
М1-Сз)
(2.6)
where Ns is the total number of spheres (or segments of the chains) in the system, Ns
= N∑iχimi, and
c = nE {°>1>2>3}∙ (2.7)
i
p ( = N∕V) is the total density of the chains formed by bonding these segments.
Figure 2.2: Schematic of chain formation from associating spherical molecules.
All previously published versions of SAFT include the term accounting for chain
connectivity (Acfcam) derived by Chapman et al. [46] on the basis of Wertheim’s theory
for associating atomic fluids. To form chains of type ‘i’, the starting point is a
39