Nanoparticle ordering in sandwiched polymer brushes

TL;DR

This paper demonstrates that ordered nanoparticle structures within sandwiched polymer layers can be achieved through mechanical compression alone, without external fields, and provides insights into controlling pattern scale via pressure and polymer length.

Contribution

The study reveals that nanoparticle ordering in polymer sandwiches can be controlled mechanically, introducing a new method for pattern formation without external fields.

Findings

Ordered structures form under compression without external fields.

Pattern scale depends on polymer length.

An approximate equation of state for nano-sandwiches is derived.

Abstract

The organization of nano-particles 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 nano-particles in between. We show that the pattern formation can be efficiently controlled by the applied pressure, while the characteristic length--scale, i.e. 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 nano-sandwiches.