Collective degrees of freedom involved in absorption and desorption of surfactant molecules in spherical non-ionic micelles

Abstract

Dynamics of absorption and desorption of a surfactant monomer into and out of a spherical non-ionic micelle is investigated by coarse-grained molecular dynamics (MD) simulations. It is shown that these processes involve a complex interplay between the micellar structure and the monomer configuration. A quantitative model for collective dynamics of these degrees of freedom is developed. This is accomplished by reconstructing a multi-dimensional free energy landscape of the surfactant-micelle system using constrained MD simulations in which the distance between the micellar and monomer centers of mass is held constant. Results of this analysis are verified by direct (unconstrained) MD simulations of surfactant absorption in the micelle. It is demonstrated that the system dynamics is likely to deviate from the minimum energy path on the energy landscape. These deviations create an energy barrier for the monomer absorption and increase an existing barrier for the monomer desorption. A reduced Fokker-Planck equation is proposed to model these effects.

New Insights into the Dynamics of Zwitterionic Micelles and Their Hydration Waters by Gigahertz-to-Terahertz Dielectric Spectroscopy

“…Understanding how micellar dynamics and structure are connected to the chemical composition and geometry of the surfactants offers a considerable challenge. Numerous theoretical approaches and simulations − have been proposed to predict structure–property relationships. Experimental techniques typically obtained by small-angle neutral scattering, static and dynamic light scattering, and cryogenic transmission electron microscopy, which can probe a wide range of length and time scales, are needed to fully characterize micelles and correlate the micellar structure to the dynamical behavior, a fundamental prerequisite for developing practical formulations.…”

Perspective on the Martini model

“…Martini simulations of micelles can also be used to provide starting structures for fine-grained models, as shown in a recent study on lyso-phospholipids, 266 and to provide details on the absorption and desorption process of non-ionic surfactants. 267 Bicelles, composed of double tail and single or short tail lipids, have also been the topic of a number of studies. 28,268,269 Carbohydrates Carbohydrates (saccharides) constitute a fundamental class of biomolecules and are present in a variety of emerging classes of biomimetic materials.…”

Formation of randomly dispersed pores in Ga-doped ZnO between Al2O3 and glass via promoted atomic diffusion: Experimental and computational study

“…MD simulation that describes the time dependent behavior of atomic/molecular systems is a widespread tool to explore the materials properties [43][44][45] and physical/chemical processes [46][47][48][49]. Despite of the limitation of its small time and length scales due to the A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 6 computational cost, it has been demonstrated that MD simulation can successfully carry out the investigations of atomic diffusivities [47][48][49].…”