(464e) Disk-Shaped Colloids: the Synthesis and Self-Assembly of Layered Crystals

Colloidal suspensions of disks are encountered in natural and industrial processes with particles ranging from clays to discotic liquid crystals to red blood cells. However, compared with calamitic systems (rods), research on liquid crystals of colloidal disks is relatively scarce due to the lack of model systems. Here, we fabricate disks via the exfoliation of layered crystals. We have performed systematic experiments on the synthesis of layered crystal α-ZrP and revealed the control of size, aspect ratio and size polydispersity of disk-shaped crystals. The growth of the disks is mediated by oriented attachment, taking place continuously throughout the hydrothermal treatment between various sized disks. We observed I-N transition at as low as 0.2% in volume fraction Φ when thickness to lateral size ratio ξ reached about 0.001. More importantly, the width of the I-N transition was observed to sensitive to the lateral size polydispersity. As our results indicate, highly anisotropic platelets, with relatively low size polydispersity, open a large range in particle concentration or volume fraction f for the formation of various phases of discotic liquid crystals. Therefore, our capability to fabricate disks/nanoplates with controlled aspect ratios, especially disks/plates with large anisotropic shape, is essential for the fully understanding of the behavior of discotic materials, and facilitating their applications.