Simulations of the Effect of Diblock Surfactant Spacer Molecules on Micelle Structure and Function

• Published in: Langmuir 1999-10, Vol.15 (22), p.7426-7431
• Main Authors: Palmer, Bruce J, Liu, Jun, Virden, Jud
• Format: Article
• Language: English
• Subjects: 40 CHEMISTRY; CONFIGURATION INTERACTION; MICELLAR SYSTEMS; MOLECULAR DYNAMICS METHOD; SURFACTANTS
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la990085l

A simple model for surfactants in solution is used to investigate the effect of diblock “spacer” molecules on the structure of micellar systems. The solvent is modeled by a simple Lennard-Jones fluid and the surfactants and spacer molecules are modeled by chains of Lennard-Jones sites connected by simple harmonic bonds. The surfactant is modeled as a solventphobic tail attached to a single solventphilic head site; the spacer is modeled as a solventphobic tail attached to a chain of solventphilic head sites. Molecular dynamics simulations on large systems (∼40 000 particles) are performed to investigate the properties of the model. The strength of the interaction between the solventphilic portion of the spacer and the solvent and the effect of the length of both the solventphobic and the solventphilic portions of the spacer on the structure of the micelle solution are investigated. The simulations suggest that for the spacer to keep micelles apart, the interaction between the solvent and solventphilic portion of the spacer must be fairly strong. Weak interactions between the solventphilic portion of the spacer and the solvent cause the spacer to collapse on the surface of the micelle.