Engineering bicontinuous cubic structures at the nanoscale-the role of chain splay

Many amphiphile-water mixtures will self-assemble into three-dimensional soft condensed structures known as inverse bicontinuous cubic phases. These structures are found in nature and have applications in nanotechnology. Here we show that by systematically varying amphiphile chain splay, we are able to control the relative stability of the inverse bicontinuous phases in a homologous series of monoglycerides in a predictable manner. In particular, we demonstrate that decreasing chain splay leads to the appearance of the primitive bicontinuous cubic phase while increasing chain splay reduces the channel size of the remaining two bicontinuous phases and tends to destabilize them with respect to the more curved inverse micellar and inverse hexagonal phases. These observations are consistent with a model in which the energetic stability of these phases is principally governed by the competing demands for homogeneous interfacial curvature and uniform chain packing and points to straightforward rules for engineering these self-assembling nanostructures.