Wetting–Dewetting and Dispersion–Aggregation Transitions Are Distinct for Polymer Grafted Nanoparticles in Chemically Dissimilar Polymer Matrix

Abstract

Simulations and experiments are conducted on mixtures containing polymer grafted nanoparticles in a chemically distinct polymer matrix, where the graft and matrix polymers exhibit attractive enthalpic interactions at low temperatures that become progressively repulsive as temperature is increased. Both coarse-grained molecular dynamics simulations, and X-ray scattering and neutron scattering experiments with deuterated polystyrene (dPS) grafted silica and poly(vinyl methyl ether) PVME matrix show that the sharp phase transition from (mixed) dispersed to (demixed) aggregated morphologies due to the increasingly repulsive effective interactions between the blend components is distinct from the continuous wetting-dewetting transition. Strikingly, this is unlike the extensively studied chemically identical graft-matrix composites, where the two transitions have been considered to be synonymous, and is also unlike the free (ungrafted) blends of the same graft and matrix homopolymers, where the wetting-dewetting is a sharp transition coinciding with the macrophase separation.

Scaling Laws for Polymer Chains Grafted onto Nanoparticles

“…The power for both good solvents falls between the good solvent prediction and the theta solvent prediction of 1/2. This could be related to the fact that there is actually a gradient of swelling observed along r and a gradual transition of v from 3/5 to 1/2 with decreasing solvent quality when higher order virial terms are considered . Clearly, these results cannot distinguish the Flory scaling prediction of 3/5 from the more accurate power of 0.588 determined by simulation …”

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] …”

Transition from Confined to Bulk Dynamics in Symmetric Star–Linear Polymer Mixtures

“…The addition of linear chains to soft colloidal suspensions is considered to be a facile and effective way to tailor the stability of nanoparticles, 20 the flow and the microscopic dynamics at rest of colloids. 11,15,[21][22][23][24][25][26][27] In contrast to hard colloids, when chains are added to suspensions of soft particles, the latter may deform and compress due to the osmotic pressure exerted by the chains and by the colloids themselves and their low elastic modulus. 15 Hence the problem of linear chain confinement becomes more complex, being dependent on the elastic modulus of the particles.…”