Numerical Simulation of Structure Formation of Surface-Modified Nanoparticles during Solvent Evaporation

Abstract

The structure formation of surface-modi ed nanoparticles during solvent evaporation is investigated by numerical simulation based on the discrete element method (DEM). The interaction forces induced by surface modi ers are considered, in addition to the contact force, Brownian force, capillary force, van der Waals force and hydrodynamic drag force. The e ects of the solvent, the surface modi er and the surface coverage of the modi er on the structure formation process during solvent evaporation and the nal structure of the nanoparticles on the substrate are clari ed. When the a nity between the solvent and the surface modi er is high, the surface-modi ed nanoparticles are well-dispersed in the solvent and the structures of nanoparticles tend to be well-ordered after solvent evaporation. On the other hand, when the surface coverage of the modi er is fairly high, the nal structures of surface-modi ed nanoparticles are relatively disordered even though the nanoparticles are dispersed in the solvent. Such a structure formation mechanism is explained based on the force curve between two nanoparticles during solvent evaporation.

Azeotropic Binary Solvent System Containing Nonfluorinated Polymer-Grafted Silica Nanoparticles for the Fabrication of a Superhydrophobic Surface

“…As the droplet evaporated, the solvent gradually evaporated on the substrate until it was completely dry, enabling a transformation in the solvent composition that could facilitate the aggregation of nanoparticles in the colloidal droplets. , To investigate the solvent composition, a simple distillation apparatus was employed to separate the solvent in the dispersion (Figure S1), and the first three condensed solvent droplets were collected and analyzed through 1 H NMR spectroscopy, as shown in Figure S2.…”

“…However, controlling the aggregation state of NP in the solvent system is crucial for the formation of deposited structures after completely drying, which can be achieved through the solvent solubility. − The phenomenon is particularly important for the polymer-grafted NP (also known as hair NP [HNP]). − At low grafting densities, the configuration of long-chain polymer brushes grafted on the surface of NP transforms between collapse and stretching (swelling) due to changes in the solubility of the solvent components. − This conformational transition affects the interactions between the HNP and solvents, thus promoting effective dispersion/aggregation. The stimulus responsiveness of HNP makes it possible to generate complex surface structures by colloidal deposition methods. − One powerful technique for preparing HNP with grafting brushes capable of conformational transitions is surface-initiated atom-transfer radical polymerization (SI-ATRP), which offers precise control over the molecular weight and architecture of tethered polymers by growing polymer chains from immobilized initiators on the particle surface.…”

Propolis particles incorporated in aqueous formulations with enhanced antibacterial performance

“…Concentrating the propolis content in the dispersions via water evaporation (from 7% to 15%) reveals a consistent and statistically significant increase ( p < 0.05 for all sonication times). Particles move in a Brownian motion and tend to collide and flocculate ( Singer, Barakat, Mohapatra & Mohapatra, 2019 ), which can be further enhanced at smaller sizes due to the higher surface area created ( Usune et al., 2019 ). Although solvent evaporation is used as means to concentrate formulations ( Avgoustakis, 2004 ; Vauthier, Cabane & Labarre, 2008 ), aggregation can be a result ( Vauthier et al., 2008 ) due to an increased likelihood of particles colliding.…”

Particle-scale modeling of the drying characteristics of colloidal suspensions

“…The aggregation is thus preferable to reduce the drying time, while the final dried structure would be loose and disordered. 25 To improve the density and order of structures with reducing the drying time by aggregation, further investigations considering the effects of morphology and strength of the aggregates would be required. Note that the present finding will be true for filtration.…”

“…We describe the Brownian motion of the particles by the Langevin equations and solve them numerically. For the i-th particle, the time evolution of the velocity v i and the position r i is expressed by 18,[23][24][25]…”