Molecular Dynamics Simulations of Cetyltrimethylammonium Bromide (CTAB) Micelles and their Interactions with a Gold Surface in Aqueous Solution

José Da Silva,Mario Meneghetti,Thereza Soares,Gabriel Da Hora,Roberta Dias

doi:10.21577/0103-5053.20170130

José Da Silva, Mario Meneghetti + Show 3 more

Open Access

https://doi.org/10.21577/0103-5053.20170130

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Abstract

Surfactants are molecular structures with remarkable physicochemical properties and applications. Most of their characteristics are due to their ability to promote aggregation and interactions with different interfaces. The scarcity of theoretical studies dedicated to evaluating the forces involved in these interactions prompted us to propose other models capable of reproducing the experimental data in better ways. We carried out molecular dynamics (MD) simulations to obtain a model for cetyltrimethylammonium bromide (CTAB), selected from gromos54a7 force field parameters, that better describes most of its behaviors in aqueous solution (micellar structure, counterion dissociation, etc.) and its adsorption pattern on a gold surface. The parameters adopted for one of the models were able to mimic several characteristics suggested by experimental measurements of the CTAB micelles, as well their adsorption pattern on a gold surface. Indeed, this model was able to obtain quasi-spherical micelles, as well as a pattern of adjacent cylindrical micelles with alkyl chain interactions on a gold surface.

Highlights

Surfactants are a class of compounds containing a polar group, charged or neutral, attached to a long hydrophobic tail.[1,2] These are remarkably versatile compounds with a broad variety of important applications in the pharmaceutical, medical, and food industries and for nanomaterial synthesis.[3,4] Above a certain temperature in solution, surfactants tend to aggregate to minimize unfavorable interactions between the surfactants and the surrounding environment.[5]
We present some aspects of Cetyltrimethylammonium Bromide (CTAB) micelles adsorption pattern on a gold surface
We demonstrated that the selection of suitable parameters is quite important for producing a micellar structure in solution and modeling its interactions with other interfaces

Summary

Introduction

Surfactants are a class of compounds containing a polar group, charged or neutral, attached to a long hydrophobic tail.[1,2] These are remarkably versatile compounds with a broad variety of important applications in the pharmaceutical, medical, and food industries and for nanomaterial synthesis.[3,4] Above a certain temperature in solution (the Krafft temperature), surfactants tend to aggregate to minimize unfavorable interactions between the surfactants and the surrounding environment.[5]. Considering that no holes exist within a micelle, its radius is estimated as the maximum extension of a hydrocarbon chain and can be evaluated by using the following equation: lmax = 0.15 + 0.1265nC (1). Where lmax is the maximum length in nm and nC is the number of carbon atoms in the chain.[19] under the previously mentioned conditions, lmax plus the length of Molecular Dynamics Simulations of Cetyltrimethylammonium Bromide (CTAB) Micelles

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