University of Lincoln, UK

Structure and phase behaviour of surfactant-water mixtures

Status: 2005 –  active

Support: UCLan

Abstract

Bead-stick images of L phase (90%). Dark blue represents head beads, light blue represents water beads and red represents tail beads.

The structure and phase behaviour of concentrated surfactant-water and polymer-water mixtures which form lyotropic liquid crystal mesophases are being studied. In particular, work is focused on intermediate phases (bilayers disrupted by water filled pores) with minimal curvature surfaces and the effects of molecular additives including oils, and anaesthetics. Dissipative Particle Dynamics  simulation is used to investigate the ability of small oil molecules (hexane, dodecane and octadecane) to control phase structures in non-ionic surfactant-water systems. The model was successfully tested against the experimental results for binary and ternary systems where the third components are “swelling” and “penetrating” oils.

Bead-stick images of H1 phase (60%). Dark blue represents head beads, light blue represents water beads and red represents tail beads.

The experimentally observed phases present in such systems were successfully modelled. In addition the simulations show the locations of the oil molecules within the bilayer and the surfactant chain conformation. Whilst the simulations confirm much of what is expected from experiment and theoretical models, evidence is found for the terminal methyl end of the surfactant molecules being located slightly closer to the interfacial region than other groups in the same chain.

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