Polymeric Solvation Shells around Nanotubes: Mesoscopic Simulation of Interfaces in Nanochannels

Abstract

Interfacial interactions in biphasic polymeric fluids confined in a nano-channel are studied using dissipative particle dynamics. The effects of an arrested nanotube at the interfaces of short-chain polymer models are elucidated and its interactions with the polymers are varied systematically. The results confirm the experimental notion that a particle can bear an excess of anisotropic interfacial stresses and consequently stabilize interface curvatures. In the presence of limited capillary effects in nanofluidic channels, the solvation shells in the vicinity of the nanotube and their related interactions become more dominant. The solvation shells are characterized by the density oscillations around the nanotube. While the oscillation intensity depends on the polymer-nanotube interactions, its characteristic length is only a function of the molecular structure of the polymer. The oscillations disappear within a certain number of shells away from the nanotube that is comparable to experimental values for low molecular weight liquids. Detailed analyses of the interface shape based on capillary wave theory reveal the impacts of such solvation forces. This study offers insights into how the polymeric solvation shells around nanoparticles can influence the interface shape, the nanoparticle-nanoparticle interactions, as well as the nanoparticle-wall interactions. Our findings can lead to promising applications in nanofluidics and in drug delivery using nanoparticles.

Modification of Interfacial Interactions in Ceramic-Polymer Nanocomposites by Grafting: Morphology and Properties for Powder Injection Molding and Additive Manufacturing

“…Computational simulation methods such as atomistic molecular dynamics (MD), Monte Carlo (MC) and dissipative particle dynamics (DPD) are useful tools in the study of the polymer-filler adhesion and the characterization of the interface between both materials [15,[29][30][31][32][33][34]. Moreover, MD simulations have been employed to study the interface between ceramic oxide fillers and polymer chains with grafted maleic anhydride or acrylic acid (AA) [30].…”

“…Polymer nanocomposites are complex systems, whose properties are determined by the properties of the components, the composition, the interfacial interactions and the morphology of the composite [13][14][15]. The adhesion and wetting of the polymer matrix to the surface of the powder [9,16] is a critical aspect since a poor adhesion will lead to the separation of both materials during processing, resulting in a weak interface and poor macroscopic properties [16,17].…”

Local Structural Fingerprints of Nanoparticle-Bound Polymer Layers

“…Adsorption of liquid-like molecules on a wetting solid surface leads to local density oscillations. ,,− ,, In extreme cases of liquid films nanoconfined to less than 10 nm thickness, such oscillations translate to completely secluded molecular layers as if the liquid molecules exist in quantized states, i.e., the so-called solvation effect. ,− The physical correlation between the adsorbed layer density (hence the molecular structures of layers) and the mechanical response of films has been the topic of ongoing theoretical as well as experimental investigations. , In recent research, similar ideas have been adopted to describe the adsorbed layers of solvents around NPs, i.e., the solvation shells. − Density profiles of the simulated polymers around the NP are plotted in Figure . With the NP fixed at the center of the plane, one can distinguish at least three adsorbed layers around the NP.…”

“…Once these layers dominate the entire thickness of the liquid film (typically at film thicknesses below ∼7 nm), the confining forces (i.e., the solvation forces) can take a decaying oscillatory functional form, as it is measured by a surface forces apparatus (SFA) for a number of different liquids . Such observations motivated the definition of solvation forces, and consequently, their underlying density oscillations at liquid–solid interfaces, in terms of a similar functional form. , Thus, the density oscillations around the NP are modeled by a combination of cosine and exponential functions as In this model, ρ 0 is the maximum density, λ is the characteristic decay length, and d 0 is the layer (shell) thickness. The fitted curves of simulation results using this model are shown in Figure .…”

“…72 Such observations motivated the definition of solvation forces, and consequently, their underlying density oscillations at liquid−solid interfaces, in terms of a similar functional form. 68,72 Thus, the density oscillations around the NP are modeled by a combination of cosine and exponential functions as…”