Figure 4.4: Comparison of the density profiles of head segments (gray), tail segments
(black) and solvent molecules (dashed gray) from modified iSAFT (curves) and molecular
simulation (symbols: head segments (■), tail segments (∙) and solvent molecules (♦)) for
a solution of: (a) repulsive chains in a repulsive solvent near a repulsive wall with a bulk
density of p⅛σ3 = 0.709 and solvent fraction xs = 0.630, and (b) attractive chains in an
attractive solvent near an attractive wall with a bulk density of ∕⅛σ3 = 0.683 and solvent
fraction xs = 0.635. The simulation results are from Frischknecht and Frink [118].
In the second case (case AA) attractions are switched on between the segments in
the Hpid molecule and also between surface and the segments (C, = 1). All head-head,
head-tail and tail-tail are uniformly attractive. Figure 4.3b compares the results from
modified iSAFT with molecular dynamics results for this case. Again the agreement is
excellent. Hence, modified iSAFT is able to correctly incorporate the packing effects
of different size segments in the lipid molecule.
To test the ability of the theory to incorporate the effect of a solvent, both these
cases RR and AA are considered in the presence of a solvent. In RR case, the solvent
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