Deactivating Symmetry Breaking of a Soft Frank-Kasper Phase via Water-Induced Conformational Ordering of a Shapeshifting Dendritic Amphiphile.

Water guides biomolecules to their native conformations in a high-dimensional conformational space. To explore a similar role in synthetic self-assembly, a wedge-shaped, shape-shifting dendron (SD) was studied. Cooling from the isotropic melt trapped SD in a metastable Frank-Kasper σ phase with symmetry breaking due to high conformational freedom. In situ SAXS, microbeam SAXS, and ATR-FTIR confirmed that water vapor disrupts supramolecular micelles in the σ phase and unfolds some cone-shaped SD molecules, facilitating improved chain-chain packing and inducing the low-symmetry σ phase to transition into a more symmetric hydrated lamellar (Lw) phase. The water-induced conformational ordering of the SD thus enables a rare σ → Lw phase transition, initially blocked by the SD's hydrophilic volume fraction. Spectroscopy results also illustrated that during the conformational ordering, water molecules are encapsulated into the hydrophilic domains of the ordered phases, enhancing the phase stability of the Lw phase and the hydrated quasicrystalline DDQC and σ phases that evolved from the Lw phase. These findings reveal a novel self-assembly pathway for the wedge-shaped amphiphile that deactivates the symmetry breaking in the Frank-Kasper σ phase and emphasize the role of water in guiding synthetic molecules to their optimal supramolecular structures, echoing the self-assembly principles in nature.