Title

Effect of packing parameter on phase diagram of amphiphiles: An off-lattice Gibbs ensemble approach

Comments

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Keywords

Monte-Carlo-Simulation; Thermodynamic Perturbation-Theory; Molecular-Dynamics Simulations; Multiple Bonding Sites; Computer-Simulations; Surfactant Solutions; Micellar-Solutions; Solvent; Mixture; Chain Molecules; Statistical Thermodynamics; Physics, Atomic, Molecular & Chemical

Abstract

We determine the phase diagram of several amphiphilic molecules as a function of the amphiphilic parameter alpha defined as the ratio of the volume of hydrophilic to hydrophobic segments using the Gibbs ensemble Monte Carlo method supplemented by configurational bias scheme. Specifically, we study amphiphilic molecules h(1)t(7), h(2)t(6), and h(3)t(5), for which alpha=0.14, 0.33, and 0.60 respectively, and demonstrate that the former two exhibit phase separation while h(3)t(5) forms micelles, supporting the contention that alpha=0.5 is the border line for phase separation and micellization, as observed in previous lattice Monte Carlo studies [Panagiotopoulos , Langmuir 18, 2940 (2002)]. Further, we study the phase separation in amphiphilic molecules as a function of the packing parameter by varying the size of the hydrophilic head for each molecule. We find that a larger hydrophilic head lowers the critical temperature T(c), and raises the critical density rho(c). (c) 2007 American Institute of Physics.

Publication Title

Journal of Chemical Physics

Volume

127

Issue/Number

24

Publication Date

1-1-2007

Document Type

Article

Language

English

WOS Identifier

WOS:000243049400006

ISSN

0021-9606

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