The name is absent

the solvent and the brush height decreases further. As the solvent density is large,
the solvent chains penetrate into the brush, as seen in figure 6.5b. However, near
the wall the brush monomers dominate, where there is a strong layering due to the
presence of the hard surface.

6.3.3 Interaction between two grafted monolayers in the ab-
sence of free polymer

Now, consider two grafted monolayers in the absence of free polymer. The struc-
ture and thermodynamic properties of the monolayers depend on the number of
segments (N_g) in the grafted chains and their grafting density (p_g). As the seg-
ments of the chains are purely repulsive, the chains are implicitly in good solvent
condition. Figure 6.6 shows the segment density profiles of the two monolayers
(N_g = 101,p_gσ² — 0.03) at different separations, H = 70 σ and H = 50 σ. Since
the brush height of both of them is about 38 σ, their free ends are in contact at H =
70 σ. At smaller separations, they interpenetrate and compress each other, as shown
in the figure for H = 50 σ. Figure 6.7a compares the total segment density profiles
of both the grafted monolayers calculated from modified iSAFT with the simulation
results of Murat and Grest [247], at different separations. In this figure, the normal
distance z is scaled by the separation H between the grafted surfaces. Modified iSAFT
is in good agreement with the simulations results. At H = 30 σ, the monolayers are
highly compressed. The total segment density increases everywhere between the two

163

<<   172   173   174   175   176   177   178   >>

More intriguing information