О 5 10 15 20 25 30
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Figure 6.1: (a) Segment density profile of hard chains tethered to a hard wall for Ng — 50
and ρgσ2 = 0.1. Ng is the number of segments in the chain and pg is the grafting density,
which is the number of chains grafted per unit area of the wall, (b) Segment density profiles
of hard chains tethered to a hard wall for Ng = 100 and pgσ2 = 0.03 (■), 0.07 (A) and
0.1(∙). Symbols are the simulation results from Grest and Murat [230] and curves are the
predictions from modified iSAFT.
the dimension along which there is inhomogeneity in the chain structure is normal
to the surface (z). Figures 6.1a and b show the density profile of polymer brushes
at different grafting densities. At lower grafting densities the profiles are parabolic,
and in good qualitative agreement with previous SCFT results [227]. However, at
high grafting densities the profiles become flatter than a parabola. The quantitative
comparison is made with the results from molecular dynamics (MD) simulations by
Grest and Murat [230]. As can be seen from figures 6.1a and b, the predictions from
modified iSAFT are in good quantitative agreement with the simulation results.
Figure 6.2a shows the density profile of these polymer brushes (having different
chain lengths) as a function of the distance from the grafting surface scaled by the
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