(558a) Effect of Surfactant Architecture on Micelle Formation and Interfacial Tension from iSAFT Molecular Density Functional Theory

Haghmoradi, A., Rice University
Miller, C. A., Rice University
Wang, L., Rice University
Hirasaki, G. J., Rice University
Chapman, W. G., Rice University

reduce the interfacial tension making them an important additive in a number of
industrial and commercial applications from enhanced oil recovery to personal
care products (e.g., shampoo, detergents, etc).  Amphiphilic surfactants,
consisting of hydrophilic components and hydrophobic components, have been
studied experimentally and theoretically.  Due to the distinct interactions
between these two components and its surrounding molecules, surfactants can self-assemble
to form interesting microstructures, i.e. micelles, monolayer, etc, in the bulk
phase as well as at the interface.  For enhanced oil recovery, surfactants of different molecular
architecture as well as formulations are studied experimentally to create the
middle phase micro-emulsion phase that produces ultra-low interfacial
tension.  The trial and error experiments needed to produce the
microemulsion phase can be minimized by developing a theory that provides
insight into the system behavior.

A density
functional theory, also known as interfacial Statistical Associating Fluid
Theory (iSAFT), has been developed and utilized to study complex inhomogeneous
fluids.  In comparison with molecular simulation, the iSAFT free energy
functionals accurately predict molecular scale structuring while including the
effects of hydrogen bonding and molecular size and shape.  In the current
work, iSAFT is applied to study micelle formation of surfactants. The
dependence of micelle structure on the surfactant architecture and formulation is
obtained.  Further, the elements necessary to produce ultra-low interfacial
tension are investigated.

1. Density Profile of Micelle in Water