Liquid Crystal Formation in Suspensions of Hard Rodlike Colloidal Particles: Direct Observation of Particle Arrangement and Self-Ordering Behavior

We successfully prepared monodisperse, hard rodlike colloidal particles with a wide range of length-to-width ratios ($L/W$). In their suspensions liquid crystals, or nematic ($N$) and smectic (Sm) phases, spontaneously appeared. The size of the particles made it possible to directly observe their arrangement and dynamics with an optical microscope. The phase behavior observed exhibited an $I$ (isotropic)-Sm transition for $L/W=3.5–8.0$ and $I\mathrm{\text{−}}N\mathrm{\text{−}}\mathrm{\text{Sm}}$ transitions for $L/W=10–35$. In pre-Sm transition regions, lateral clustering of the particles and subsequent layering of the clusters were observed exactly.