Study On The Discotic Liquid Crystal Phase Behaviors Of Zirconium Phasphate Nanoplates

Colloidal suspensions of disks and plates are abundant in the nature and industrial products, such as clay, asphalts, red blood cells and discotic liquid crystal solar cell. Despite their abundance and wide industrial application, disks are the least studied compared to spheres and rods, due to the lack of modeling systems. In this research, we will use the monolayers ZrP nanoplates,which are identical in thickness and diameter controllable, as a model system to study the phase behaviors of discotic colloidal li quid crystals. Details are follows:1. The crystalline α-ZrP were synthesized by a hydrothermal method, and exfoliated with TBAOH into monolayers. Later, we studied the effect of temperature on the phase behavior of discotic liquid crystals. The results showed that the onset concentration φ of I-N phase transition increases with increase of temperature. In the meantime, the biphasic gap broadens with increasing temperature. Analysis showed that, for charged ZrP monolayers,εrT decreases as the temperature increases, resulting in Nematic phase melting and φ1 increasing. We also observed that at higher temperatures, the I-N phase transition is more sensitive to polydispersity of the size of the nanoplates.2. Different size of ZrP nanoplates were synthesized by hydrothermal synthesis method and reflux method. The polydispersity of plates were controlled by I-N phase transition fractioning. We drew the I-N phase transition diagram at different diameter and observed the impact of the diameter of discotic to the I-N phase separation rates. The results showed that,φ1 of I-N phase transition decreased with the increase of the diameter of plates, and the rate of I-N transition increased with the decrease of the diameter. This is because the orientation of larger platelets change more easily, and the I-N phase transition occurs first with a larger platelet size. For the smaller platelets, due to its rapid rate of Brownian motion, they form ordered structures faster, so the speed of I-N phase separation is faster.3. The ionic strength of discotic liquid crystal was changed by TBA+Cl-molecules. We studied the effect of ionic strength on the phase behavior of liquid crystals. And found that the I-N phase separating rate was faster with increasing ionic strength. The φ1 of I-N phase transition increased first and then decreased with increasing of ionic strength. Explanation could be the effective volume of platelets and the electrostatic repulsion between platelets decreased with increasing ionic strength. The formation of Nematic phase was restricted with decreasing of the effective volume of platelets, and promoted with decreasing of the electrostatic repulsion. At low ionic strength of the suspension, the effect of increasing ionic strength was dominated by the decreasing of the effective volume, and the formation of Nematic phase was restricted. When the ionic strength of the suspension reaches a certain high value, the effect of increasing ionic strength was competed by the decreasing of electrostatic repulsion, which enhances the anisotropy of the platelets, promoting the formation of N phase and φ decreased. The decrease of the effective volume accelerated the rate of movement of the platelets, so I-N phase separating rate became faster.