Morphological Control of Grafted Polymer Films by Nanoparticle Binding

TL;DR

This study investigates how nanoparticles influence the morphology of grafted polymer layers, revealing phase transitions driven by nanoparticle attraction strength, with implications for nanomaterial design and biological systems.

Contribution

It introduces a combined theoretical and simulation approach to analyze morphological transitions in nanoparticle-decorated polymer layers, highlighting a novel first-order phase transition mechanism.

Findings

Nanoparticles induce large morphological changes in polymer layers.

A first-order phase transition occurs at strong polymer-nanoparticle attraction.

Results align qualitatively with protein binding behaviors in biological systems.

Abstract

Mixtures of nanoparticles and polymer-like objects are encountered in many nanotechnological applications and biological systems. We study the behavior of grafted polymer layers decorated by nanoparticles that are attracted to the polymers using lattice gas based mean field theory and accompanying coarse-grained Brownian dynamics simulations. We find that the presence of nanoparticles can induce large morphological transitions in the layer morphology. In particular, at moderate nanoparticle concentrations, the nanoparticles cause a reduction in the height of the polymer layer above the grafting surface, which occurs via a novel first-order phase transition for sufficiently strong attraction between the polymers and the nanoparticles and smoothly for weak attractions. The predictions of the theory qualitatively agree with the observed behavior of grafted natively unfolded protein strands upon binding of proteins. The results also inform ways of designing nanopolymer layer morphologies.