Figure 6.14: (a) Locus of the critical value of a at which the interaction force between
the grafted monolayers becomes attractive for different relative segment sizes of the grafted
and free polymers: σg — σy(B), σg — l.lσ∕(∙), and σg = 1.2σj(⅛). The bulk free polymer
density, pf σ j = 0.6 and Ns = 101. σf = σ. (b) Scaling relation for the locus of the critical
value of a for different relative segment sizes of the grafted and free polymer: Ng = 101, σg =
σy(B); Ng = 101,σg = l.lσ∫(∙); Ng = 101,σs — 1.2σ∕(∆); and Ng = 151,σg = σ∕(⅜)∙
σf = σ. The bulk free polymer density, Pfσj = 0.6. σy = σ.
the critical value of a where the interaction force between the two monolayers turns
from purely repulsive to attractive follows the scaling relation, pgy∕Ngβ3 oc a~2.
6.4 Conclusions
Modified iSAFT density functional theory has been extended to study the struc-
ture of polymer brushes in the absence∕presence of free polymer solvent. In the
absence of the solvent or for ‘dry brush’, the structure is governed by the grafting
density and the segment-segment interactions of the polymer chain. The theory is in
good quantitative agreement with the MD simulation results in literature and follows
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