Simple and Complex Micelles in Amphiphilic Mixtures: A Coarse-Grained Mean-Field Study

Abstract

Binary mixtures of amphiphiles in solution can self-assemble into a wide range of structures when the two species individually form aggregates of different curvatures. In this paper, we focus on small, spherically-symmetric aggregates in a solution of sphere-forming amphiphile mixed with a smaller amount of lamella-forming amphiphile. Using a coarsegrained mean-field model (self-consistent field theory, or SCFT), we scan the parameter space of this system and find a range of morphologies as the interaction strength, architecture and mixing ratio of the amphiphiles are varied. When the two species are quite similar in architecture, or when only a small amount of lamella-former is added, we find simple spherical micelles with cores formed from a mixture of the hydrophobic blocks of the two amphiphiles.For more strongly mismatched amphiphiles and higher lamella-former concentrations, we instead find small vesicles and more complex micelles. In these latter structures, the lamella- Simple and complex micelles in . . . be large, and the implications of this for the solubilization of hydrophobic chemicals are considered. The mechanisms behind the formation of the above structures are discussed, with a particular emphasis on the sorting of amphiphiles according to their preferred curvature.

The self-assembly of linear–dendritic and lipid-like copolymers investigated by computer simulations

“…It well satises the widely accepted rule that with the increase of the hydrophilic volume fraction, the aggregations change from lamellar structures to micelles. 9,10 The detailed morphologies and the mechanism of the morphological changing from the compound vesicles to network micelles will be discussed in the following. Table 1 The interaction parameters of bead-bead pairs, a ij (k B T/r c ) During the self-assembly, the randomly mixed amphiphiles rst aggregate to small disk-like micelles driven by their hydrophobic interactions.…”

“…Therefore, it is important to regulate the self-assembled nanostructures and predict their specic functions from the building molecules. Previous studies [7][8][9][10] found that the self-assembled structures of amphiphiles are denitively determined by their architectures, such as the size of the hydrophilic and hydrophobic components. Generally, if the hydrophilic part is larger than the hydrophobic part, the micelles form.…”

Benchmarking a self-consistent field theory for small amphiphilic molecules

“…In eqn (1) and ( 2), V HT (r) is the (effective) repulsive interaction between heads and tails of distinct molecules. V conn (r) in eqn (5) for the propagator G(r,r 0 ) is the connectivity potential between heads and tails within a single molecule. These two potentials will in general be chosen to reflect properties of the amphiphilic molecules.…”

“…Other dynamic [6,7,9,35,36] or lower dimensional SCFT studies [5,8,9,37] have also pointed towards a universality of behaviour between lipids and amphiphilic block copolymers.…”

“…25,26 Comparisons with simulations using widely different models for lipid molecules show a universality of behaviour that is in agreement with their approach. 25 Other dynamic 6,7,9,35,36 or lower dimensional SCFT studies 5,8,9,37 have also pointed towards a universality of behaviour between lipids and amphiphilic block copolymers.…”