Interconversion of Triply Periodic Constant Mean Curvature Surface Structures: From Double Diamond to Single Gyroid

Abstract

Triply periodic constant mean curvature surface structures have been discovered in a variety of biological and self-assembly systems. Among them, the single gyroid is of significant interest, because of its unique geometry, inherent chirality, and corresponding spectacular optical properties. Despite theoretical and experimental efforts on this structure, so far, limited progress has been made regarding the formation of the single network structures and the structural relationships with the thermodynamically stable double networks. Herein, we report the electron microscopic observation and analysis on the interconversion between the single gyroid and double diamond structure in an amphiphilic ABC triblock terpolymer templated macroporous silica synthesis system with a solvent mixture of tetrahydrofuran and water. The two structures were interconnected by a "side-by-side" epitaxial relationship with rescaling of the unit cell. The single-network structure was formed via a new type of alternating gyroid under the restricted epitaxial intergrowth, in which the hydrophilic block with the silica source and the solvent tetrahydrofuran formed the two chemically distinct, interpenetrating gyroid networks of opposite chirality in a matrix of the hydrophobic block