Polydispersity for Tuning the Potential of Mean Force between Polymer Grafted Nanoparticles in a Polymer Matrix

Abstract

We present an integrated theory and simulation study of polydisperse polymer grafted nanoparticles in a polymer matrix to demonstrate the effect of polydispersity in graft length on the potential of mean force between the grafted nanoparticles. In dense polymer solutions, increasing polydispersity in graft length reduces the strength of repulsion at contact and weakens the attractive well at intermediate interparticle distances, completely eliminating the latter at high polydispersity index. The reduction in contact repulsion is attributable to polydispersity relieving monomer crowding near the particle surface, especially at high grafting densities. The elimination of the midrange attractive well is attributable to the longer grafts in the polydisperse graft length distribution that introduce longer range steric repulsion and alter the wetting of the grafted layer by matrix chains. Dispersion of the grafted particles is stabilized by increased penetration or wetting of the polydisperse grafted layer by the matrix chains. This work demonstrates that at high grafting densities, polydispersity in graft length can be used to stabilize dispersions of grafted nanoparticles in a polymer matrix at conditions where monodisperse grafts would cause aggregation.

Perspective: Outstanding theoretical questions in polymer-nanoparticle hybrids

“…22,24,26,33,37,42,50,88,90,95,109,[119][120][121][122]125,[143][144][145][146][147][148][149][150] Ganesan et al 22 have shown that the morphologies adopted by grafted NPs in a selective solvent are sensitively determined by the ratio of the NP core size to the native size of the polymeric grafts. Recent work by Jayaraman, 88,89,92 which is in good agreement with experiments, illustrates that the polydispersity of graft lengths can play a critical role in the miscibility of NPs in a polymer matrix with the same chemistry as the brush.…”

“…(i) Phase diagrams: The theoretical/simulation works of Schweizer,46,[75][76][77][78][79] Striolo,60,[80][81][82][83] Roan,84,85 Pakula, 86,87 Jayaraman, 24,37,[88][89][90][91][92][93][94][95] de Pablo, [96][97][98][99][100][101][102] Panagiotopoulos, 50,56,[103][104][105] Grest, 34,42,71,[106][107][108][109][110][111][112][113][114] …”

Confinement enhances dispersion in nanoparticle–polymer blend films

“…Extensive research has, therefore, been devoted to understand the morphological and dynamical phase diagram of such blends and the consequent role it plays in determining the physical properties of these materials [5][6][7][8][9][10][11][12][13] . On the basis of these studies, various strategies are therefore being devised to enhance the dispersibilty of various functional nanoparticles in PNCs [5][6][7][8][9][10][11][12][13][14][15] . It is believed 4,8,11,13 that a wetting nanoparticle-polymer interface is required for homogeneous nanoparticle dispersion in bulk PNCs.…”

Polymer grafted nanoparticles: Effect of chemical and physical heterogeneity in polymer grafts on particle assembly and dispersion

“…And, how does ''polydisperse grafted polymer distribution'' improve grafted particle dispersion in a matrix compared to a bidisperse grafted polymer length distribution? To address this, in a more recent study, 1 we studied effects polydispersity in graft length on the PMF between the grafted nanoparticles, varying the PDI of the grafted chains from 1 to 2.5.…”