Self-Assembly of Organophilic Nanoparticles in a Polymer Matrix: Depletion Interactions

Abstract

The dispersion of nanoparticles in a polymer matrix has been proven a challenge. A recent experiment reveals that it can be controlled by the relative size of nanoparticle/matrix polymer instead of their compatibility. Dissipative particle dynamics simulations are thus employed to investigate self-assembly of organophilic nanoparticles and dispersion of organophobic nanoparticles. The degree of aggregation in terms of the mean aggregation number is evaluated to explore the aggregation kinetics of nanocubes and nanoplatelets. The influence of the length of the matrix polymer on the aggregation behavior is studied as well. It is found that the depletion attraction plays the major role for the aggregation of organophilic nanoparticles. Large nanoplatelets prefer clustering, while small nanoplatelets tend to disperse because the depletion attraction grows with the face area of nanoparticles. On the other hand, the slow aggregation kinetics, hindered by the energy barrier associated with depletion interactions and low nanoparticle diffusivity, is responsible for the low degree of aggregation for organophobic nanoparticles.

Synthesis and Interfacial Properties of Optically‐Active Photonic Nanocomposites with Single Nanoparticle Dispersion at High Solids Loading

“…The single nanoparticle dispersion in nanocomposite obtained from solution having stood for two months is ascribed to the strong interaction between the H-POSS-PMMA and N-NPs core-shell nanoparticles which provides steric hindrance and prevent aggregation before and during the spin coating process. [ 35 ] In our experiment, the spin coating process (spin rate 6000 rpm, spin time 1 min) is rapid and the H-POSS-PMMA modifi ed nanoparticles have little chance to diffuse among the polymer molecule during solidifi cation process. energetic interactions and entropic effects) that affected the particle dispersion Adv.…”

Interparticle Forces Underlying Nanoparticle Self‐Assemblies

“…[ 125 ] Hu et al demonstrated that the dispersion or aggregation of nanoparticles is independent from the nanoparticles/polymers compatibility, but is infl uenced by depletion attractions. [ 126 ] Different from previous concepts that organophilic nanoparticles tend to disperse in a polymer matrix, depletion forces drive organophilic nanoparticles to aggregate into clusters with a nanoparticle size of larger than the polymers' radius of gyration, while small size organophobic nanoparticles could disperse in the polymer matrix. Unlike sphere particles, the depletion attractive force of nanorods is more signifi cant than that of nanospheres, due to the higher gain in the overlapped excluded volume in rods.…”

“…Baranov et al assembled hydrophobic colloidal semiconductor nanorods into monolayers of close‐packed hexagonal arrays by tuning depletion attraction forces in an organic solvent . Hu et al demonstrated that the dispersion or aggregation of nanoparticles is independent from the nanoparticles/polymers compatibility, but is influenced by depletion attractions . Different from previous concepts that organophilic nanoparticles tend to disperse in a polymer matrix, depletion forces drive organophilic nanoparticles to aggregate into clusters with a nanoparticle size of larger than the polymers' radius of gyration, while small size organophobic nanoparticles could disperse in the polymer matrix.…”

Polymer stretch in two-phase microfluidics: Effect of wall wettability

“…These polymer beads are connected by harmonic spring potentials with the spring constant k s (¼ 100 k B T=r 2 c ) and the unstretched length l s (¼ 0:7 r c ). 19 The microfluidic channel is a cylindrical tube with the radius R ¼ 10 r c . The tube wall is constructed by two layers of static particles and provides a simple bounce back condition to all fluid DPD particles.…”