Nanoparticle Organization in Sandwiched Polymer Brushes

The organization of nanoparticles
inside grafted polymer layers
is governed by the interplay of polymer-induced entropic interactions
and the action of externally applied fields. Earlier work had shown
that strong external forces can drive the formation of colloidal structures
in polymer brushes. Here we show that external fields are not essential
to obtain such colloidal patterns: we report Monte Carlo and molecular
dynamics simulations that demonstrate that ordered structures can
be achieved by compressing a “sandwich” of two grafted
polymer layers, or by squeezing a coated nanotube, with nanoparticles
in between. We show that the pattern formation can be efficiently
controlled by the applied pressure, while the characteristic length-scale,
that is, the typical width of the patterns, is sensitive to the length
of the polymers. Based on the results of the simulations, we derive
an approximate equation of state for nanosandwiches.