Six Different Assemblies from One Building Block: Two-Dimensional Crystallization of an Amide Amphiphile

A Cs-symmetric amide amphiphile containing a C18 alkyl chain exists in at least six crystalline phases at the liquid/solid interface; several of these phases display regularly arranged nanoscopic voids. Structural analysis of each phase reveals that highly symmetric and/or complex patterns arise through adopting various aggregates via noncovalent interactions, several of which are mediated by the unique hydrogen-bonding properties of the primary amide. The formation of each phase is interpreted in the context of the kinetic and thermodynamic behaviors, with some phases showing concentration-dependent stabilities, while others are purely kinetic in origin. This investigation contributes to understanding the factors that give rise to solid form diversity in two- and three-dimensional crystallization.