The name is absent

be obtained assuming that the chains are strongly stretched [196, 197, 198, 199, 200,
201, 183, 202]. Zhulina et. al. [183] used this analytical SCFT or strong stretching
theory (SST) to study the interactions between grafted colloid particles. In SST, the
grafted polymer chains assume their most probable conformations, i.e. fluctuations
around this conformation are not taken into account. However, these fluctuations
are important for the brush structure, especially at low grafting densities or shorter
chains. Hence, several research groups have applied numerical SCFT to calculate
the effective interaction between two flat grafted monolayers in the presence of free
polymer, van Lent et. al. [203] and Wijmans et. al. [204] applied the lattice version
of SCFT developed by Scheutjens and Fleer [205]. van Lent et. al. showed that the
effective interaction between the grafted monolayers not only depends on the deple-
tion of the free polymer in the monolayers, which was usually regarded as the origin
of attraction, but also on the conformational changes of the two monolayers as they
approach each other. They only considered cases where the relative degree of poly-
merization of free and grafted polymer chains (α = Ny∕N_s) is greater or equal to one.
Wijmans et. al. did more systematic study for different chain lengths and grafting
densities. Their main conclusions are: (1) for a given grafting density (p_g : defined as
the number of chains tethered to unit area of the surface), attraction occurs only when
a is greater than a critical value otherwise the interaction is purely repulsive; and (2)
the critical value of a decreases with increase in ρ_g. However, the critical values of
a or the domains of repulsion/attraction were not specifically calculated for different

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