Effective short-range Coulomb correction to model the aggregation behavior of ionic surfactants

Abstract

We present a short-range correction to the Coulomb potential to investigate the aggregation of amphiphilic molecules in aqueous solutions. The proposed modification allows to quantitatively reproduce the distribution of counterions above the critical micelle concentration (CMC) or, equivalently, the degree of ionization, α, of the micellar clusters. In particular, our theoretical framework has been applied to unveil the behavior of the cationic surfactant C24H49N2O + 2 CH3SO − 4 , which offers a wide range of applications in the thriving and growing personal care market. A reliable and unambiguous estimation of α is essential to correctly understand many crucial features of the micellar solutions, such as their viscoelastic behavior and transport properties, in order to provide sound formulations for the above mentioned personal care solutions. We have validated our theory by performing extensive lattice Monte Carlo simulations, which show an excellent agreement with experimental observations. More specifically, our coarse-grained model is able to reproduce and predict the complex morphology of the micelles observed at equilibrium. Additionally, our simulation results disclose the existence of a transition from a monodisperse to a bidisperse size distribution of aggregates, unveiling the intriguing existence of a second CMC.

Ethylcellulose nanoparticles as a new “in vitro” transfection tool for antisense oligonucleotide delivery

“…The cationic amidoammonium amphiphile, ricinoleamidopropyltrimonium methosulfate (Figure 1c), in the following abbreviated as CatA, was from Evonik. It has an active matter content of 40 wt% in water and a critical micellar concentration of 3.3 x 10 -2 mM (Burgos-Mármol et al 2016…”

Molecular Dynamics of Janus Nanodimers Dispersed in Lamellar Phases of a Block Copolymer

“…Coarse-grained models portray groups of atoms as single interaction sites, reducing the number of degrees of freedom and thus allowing the study of longer time and length scales. Even though this reductionist model lacks full chemical detail, it still proves to be an efficient method to study properties at the mesoscale such as self-assembly [ 65 , 66 ], phase behaviour [ 67 ], structure [ 68 ], dynamics [ 69 ] and viscoelastic and thermal properties [ 70 , 71 ]. Our interest is understanding how the interactions between the polymer chain and the NDs impact distribution and orientation of the particles in the lamellae and how this ordering (or lack of) influences their mobility at long-time scales.…”