Elasticity of polymeric nanocolloidal particles.

Jonas Riest,Sergei A Egorov,Christos N Likos,Labrini Athanasopoulou,Primož Ziherl

doi:10.1038/srep15854

Abstract

Softness is an essential mechanical feature of macromolecular particles such as polymer-grafted nanocolloids, polyelectrolyte networks, cross-linked microgels as well as block copolymer and dendrimer micelles. Elasticity of individual particles directly controls their swelling, wetting, and adsorption behaviour, their aggregation and self-assembly as well as structural and rheological properties of suspensions. Here we use numerical simulations and self-consistent field theory to study the deformation behaviour of a single spherical polymer brush upon diametral compression. We observe a universal response, which is rationalised using scaling arguments and interpreted in terms of two coarse-grained models. At small and intermediate compressions the deformation can be accurately reproduced by modelling the brush as a liquid drop, whereas at large compressions the brush behaves as a soft ball. Applicable far beyond the pairwise-additive small-strain regime, the models may be used to describe microelasticity of nanocolloids in severe confinement including dense disordered and crystalline phases.

Highlights

Softness is an essential mechanical feature of macromolecular particles such as polymer-grafted nanocolloids, polyelectrolyte networks, cross-linked microgels as well as block copolymer and dendrimer micelles
We use molecular dynamics (MD) simulations to study the deformation of an SPB consisting of a small hard colloidal particle grafted with a polymer brush of f linear-chain arms each consisting of Nc monomers; temperature was fixed at T = /kB where is the energy scale of the monomer-monomer repulsion
The differences between their shapes are hardly visible as seen by comparing the contours at slit width of 80% of the reference diameter dDthr*ea.TmiBhnaui-tstpicilaanatnlsllieyag,rhdgatiesasimscuomqemtuienaprngroetiafstsatpihtorievnoenstleyotnhuesenliaocabnelomd-droapotsametndiicnnaincakoteeFm-dilgipkΨ.re5e=sbsshiwba1plh0ee0i,cachdtorsnoshlspiottawiwnsstio-dtnvhtohleylsutshbmlieegeolhorΨwteltyi=aclbaaol0rgu.r0eet1rd4utd0hcr%eaodnpocDfeexD*np.t*ar,nawldhlsaetvreeerraaysl extensionζ of a diametrally compressed liquid drop for Ψ = 0.01, 0.1, 1, 10, and 100

Summary

Introduction

Softness is an essential mechanical feature of macromolecular particles such as polymer-grafted nanocolloids, polyelectrolyte networks, cross-linked microgels as well as block copolymer and dendrimer micelles. We use numerical simulations and self-consistent field theory to study the deformation behaviour of a single spherical polymer brush upon diametral compression. A interesting area is the mechanics of nanocolloids such as polymer-grafted nanoparticles and dendrimer micelles, where elastic theory can be employed to construct coarse-grained models[15] capable of capturing the many-body effects[16]. We explore this idea by probing the elasticity of spherical polymer brushes (SPBs; Fig. 1a) which interpolate between star polymers[17] and polymer-stabilised colloids. Our predictions can be explored experimentally either directly in force-deformation measurements of SPBs19 or indirectly by analysing the structure of their condensed phases and aggregates[20]

Methods

Results

Conclusion