Structure and Entanglement Network of Model Polymer-Grafted Nanoparticle Monolayers

Abstract

Ultrathin films containing polymer-grafted nanoparticles (PGNs) show promise for use in hybrid electronics and high energy density materials. In this work, we use a coarse-grained model to simulate a hexagonally packed monolayer of PGNs adsorbed on a smooth surface that is attractive to both nanoparticles and polymer chains. We find that decreasing graft density at the same graft length increases interpenetration of the polymer-grafted layers, as expected. We quantify both overall and interparticle entanglements (between polymers grafted to different PGNs). While the higher graft density particles have a higher overall number of entanglements per chain, the lower graft density particles have higher interparticle entanglements per chain due to their increased chain interpenetration. Finally, we apply uniaxial tensile deformation to the monolayers; the peak stress occurs at lower strain values for higher graft density particles, which is attributed to the relatively lower number of interparticle entanglements. Our analysis provides a molecular picture of how decreasing graft density leads to better interpenetration, increased interparticle entanglements, and increased toughness of PGN monolayers, though it can lead to slightly less uniformly spaced monolayers, in agreement with previous experimental observations. These tradeoffs are crucial to understand for the design of robust, well-ordered inorganic−organic hybrid films.

Disentangling the Role of Chain Conformation on the Mechanics of Polymer Tethered Particle Materials

“…23 Molecular dynamics (MD) simulations predicted an increase of fracture toughness with increasing chain length, implying that entanglements affect interparticle interactions. 24,25 These findings illustrate the opportunities to design hybrid material properties that are facilitated by a better understanding of the governing parameters, which control interactions in brush particle systems. However, no study has been yet able to quantitatively relate macroscopic response characteristics to microstructural features such as the distribution of tethers within the brush particle assemblies.…”

Polymer-functionalized polymer nanoparticles and their behaviour in suspensions

“…25,26 The influence of N and σ on the stability of polymer functionalized nanoparticles dispersed in a solvent or in a solid matrix has been widely studied for nanoparticles with a rigid core. In such systems, the dynamics of the nanoparticle suspensions and the particle/particle interactions in suspension were mostly governed by the architecture of the polymer canopy 27 via the excluded volume interactions and chain configuration entropy, 28,29 and fluctuations of the polymer canopy influenced the fragility of the particle assemblies. 30 Furthermore, for similar polymer canopies, the degree of swelling of the polymer canopy changes the chain conformation in the canopy and the resulting behaviour of the suspensions.…”

Polymer Adsorbents vs. Functionalized Oxides and Carbons: Particulate Morphology and Textural and SurfaceCharacteristics

“…The latter may be characterized by lower stability of the textural characteristics than stable and rigid solids due to various effects of dispersion media, swelling, aging, freezing with liquids, heating, mechanical loading, as well as due to high fractality, strongly tortuous pores, and disordered texture of nonrigid polymers [26][27][28][29][30][31][32][33][34]. Various composites [35][36][37][38], nanostructured polymers [39][40][41][42][43][44][45], polymer/oxides [46][47][48], and polymer/carbons [49][50][51][52] composites are of interest from a practical point of view. However, accurate textural characterization of polymeric composites, complex filler-polymer and filler-polymer-polymer systems is a more difficult task than a similar challenge for individual oxide, carbon, or polymeric materials.…”