Using analytical theory and self-consistent field calculations,
we study the conformation behaviors and switching properties of an
adsorption-active polymer chain with its free end attached to a hard-core
nanoparticle included in an inert brush. The conformation switches
are induced by the short-ranged adsorption from the substrate. Particularly,
we focus on the influence of particle size and quantify the switching
properties by evaluating the transition point, transition width, and
transition barrier. Our results indicate that the particle–polymer
system exhibits different phases and transition features compared
to the particle-free system only when the particle is large enough.
To characterize the particle size, we define two critical particle
radii R* and R
c. If R > R*, the particle could be stuck
at
the brush surface exhibiting a partially exposed state, which cannot
be observed in the particle-free polymer switches. On the contrary,
if the particle is small, only two states, the exposed state and the
adsorbed state, are involved. When R > R
c, the transition properties show different
dependence
on the system parameters like the grafting density of the brush, the
solvent quality, and the length of the polymer chains. Analytical
expressions for the transition point, transition width, and transition
barrier are derived. The obtained scaling formulas at the small particle
and large particle limits are verified by the self-consistent field
calculations. Our analysis concludes that a large particle attached
to the end of the active chain mainly broadens the transition width
while keeps the transition barrier as small as that in the free-particle
system as the system parameters are carefully tuned. Strong osmotic
repulsion imposed on the finite volume particle is responsible for
the particular phase and transition characteristics observed in the
present particle–polymer switches.