Self-Assembly of Nanoparticle–Surfactant Complexes with Rodlike Micelles: A Molecular Dynamics Study

Abstract

The self-assembly of nanoparticles (NPs) with cationic micelles of cetyltrimethylammonium chloride (CTAC) is known to produce stable nanogels with rich rheological and optical properties. Coarse-grained molecular dynamics (MD) simulations are performed to explore the molecular mechanisms underlying this self-assembly process. In an aqueous solution of CTAC surfactants, a negatively charged NP with a zeta potential of less than -45 mV is observed to form a stable vesicular structure in which the particle surface is almost entirely covered with a double layer of surfactants. In comparison, surfactants form a monolayer, or a corona, around an uncharged hydrophobic NP with the tailgroups physically adsorbed onto the particle. In the presence of sodium salicylate salt, such NP-surfactant complexes (NPSCs) interact with rodlike CTAC micelles, resulting in the formation of stable junctions through the opening up of the micelle end-cap followed by surfactant exchange, which is diffusion-limited. The diffusive regime spans several hundred nanoseconds, thereby necessitating MD simulations over microsecond time scales. The energetics of NPSC-micelle complexation is analyzed from the variation in the total pair-potential energy of the structures.

Aggregation behavior of Triton X-114 and Tween 80 at various temperatures and concentrations studied by density and viscosity measurements

“…On the a = f(log C) curves for TX114 and Tween 80 at T = 293 K, there are two break points-the first corresponds to the values of CMC determined from the surface tension measurements and the second is close to C = 10 -3 M. This suggests the existence of the second value of CMC of TX114 and Tween 80 in which the micelle structure changes and/or admicelles are changed into micelles [28]. It is known that amphiphilic molecules generally form spherical aggregates in aqueous solutions above the CMC, but, under certain conditions these spherical micelles grow in size or change their shape resulting in the formation of rodlike structures or even long flexible micelles [29][30][31][32][33]. It is interesting that for both surfactants at T = 293 K, the values of a decrease up to that of the first CMC, then they are almost constant at C between the first and second CMC and next grow up, especially for Tween 80.…”

Can cloud point-based enrichment, preservation, and detection methods help to bridge gaps in aquatic nanometrology?

“…For example, with the aid of these simulations, aqueous systems containing cationic surfactants were recently studied. It was shown that the surfactants form a bilayer around NPs with negatively charged surfaces and monolayers around hydrophobic NPs [ 24 ].…”

First principle study of silver nanoparticle interactions with antimalarial drugs extracted from Artemisia annua plant

“…In the context of computational materials science, first principle Density Functional Theory (DFT) calculations allow the prediction and calculation of material behavior on the basis of quantum mechanical considerations, without requiring higher-order parameters such as fundamental material properties (Pakiari and Jamshidi 2007;Granatier et al 2007;Aliakbari Tehrani et al 2012). Alongside DFT, molecular dynamics (MD) simulation is a powerful computational method that can analyze the interactions between species in a system in atomistic level and reveals problems that are not observable experimentally (Antuek et al 2003;Sambasivam et al 2016). However, a recourse to MD simulation was needed to evaluate the interaction of drug and AgNP to predict the affinity sites of the drug to interact, which is a useful concept in designing effective combination for drug delivery purposes (Yousefpour et al 2018;Kordzadeh et al 2019).…”