Stabilizing Photonic Colloidal Smectic-A Liquid Crystals through Enthalpic Patches

Photonic crystals are valuable for controlling light but typically require complex lithography or precise self-assembly. Colloidal smectic liquid crystals offer a promising alternative by forming periodic structures without intricate manipulation, yet achieving them at low particle densities remains challenging. Here, we propose a facile strategy for stabilizing the colloidal smectic phase at low particle densities through the self-assembly of tip-patched colloidal ellipsoids. As the patch–patch attraction increases, the nematic-to-smectic-A phase transition occurs at lower densities, and sufficiently strong attraction results in a direct isotropic-to-smectic-A transition. Enthalpic-patch-induced dimers and trimers play a crucial role in stabilizing the colloidal smectic-A phase. Moreover, optical property calculations reveal that the obtained colloidal smectic-A phase exhibits bright structural colors with high reflectance, which can be tuned by adjusting the size of the colloidal ellipsoids. These findings suggest a straightforward route to achieve advanced photonic materials by strategically introducing enthalpic patches in systems of anisotropic ellipsoids.