Structure of Polymer Layers Grafted to Nanoparticles in Silica–Polystyrene Nanocomposites

Abstract

Abstract:The structural features of polystyrene brushes grafted on spherical silica nanoparticles immersed in polystyrene are investigated by means of a Monte Carlo methodology based on polymer mean field theory. The nanoparticle radii (either 8 nm or 13 nm) are held constant, while the grafting density and the lengths of grafted and matrix chains are varied systematically in a series of simulations. The primary objective of this work is to simulate realistic nanocomposite systems of specific chemistry at experimentally accessible length scales and study the structure and scaling of the grafted brush. The profiles of polymer density around the particles are examined; based on them, the brush thickness of grafted chains is estimated and its scaling behavior is compared against theoretical models and experimental findings. Then, neutron scattering spectra are predicted both from single grafted chains and from the entire grafted corona. It is found that increasing both the grafting density and the grafted chain molar mass drastically alters the brush dimensions, affecting the wetting behavior of the polymeric brush. On the contrary, especially for particles dispersed in high molecular weight matrix, variation of the matrix chain length causes an almost imperceptible change of the density around the particle surface.

Melt-grafting for the synthesis of core–shell nanoparticles with ultra-high dispersant density

“…Such high grafting densities should give rise to a brush density profile on the NPs that is unique, 26,27 and which is under further experimental investigation. Grafting of dense shells on such NPs requires replacement of the strongly physisorbed oleic acid remaining on the particle surface after synthesis; this has hitherto not been achieved and prevented biomedical application.…”

Understanding the role of grafted polystyrene chain conformation in assembly of magnetic nanoparticles

“…Theodorou has simulated single chain and corona scattering for different surface densities and graft lengths [14]. Their simulation results, however, did not validate the collapse of corona observed in high molar mass matrices as reported in the experimental findings of Chevigny [13].…”

Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method

“…[13][14][15][16] Specifics of NP-PB adhesion were explored by a number of different computational approaches, in particular with self-consistent field theory (SCFT), 17,18 molecular dynamics (MD), 19,20 Brownian dynamics (BD), 21 and Monte Carlo (MC) simulations. [22][23][24] Of our particular interest are theoretical and computational studies of the free energy of NP-PB interactions, which is determined by interplay of enthalpic attraction due to polymer adsorption at NP surface and entropic repulsion due to restrictions on conformations of the polymer chains a) Author to whom correspondence should be addressed. Electronic mail:…”