Abstract

Background: This work is broadly motivated by the perspective of the development of ferroelectric liquid crystal devices and the need to develop a basic understanding of the wetting properties of these strategic materials. Surface stability and wetting properties of smectic C* ferroelectric liquid crystal mixture was experimentally studied using highly polarized reflected optical microscopy.

Method: A thin film samples of smectic C* ferroelectric liquid crystal mixture on soft silicon dioxide substrate were prepared using a homemade spin-coated machine with a thickness of 300 nm and 600 nm. Images were taken on heating and cooling processes, with heating rate 0.5 ^oC/min.

Results: The results showed the following: a) the thin film samples composed from multilayer, b) in both film thickness samples the dewetting started a few degree ^oC below the bulk SmA to the isotropic phase transition temperature, c) in both samples undulation was observed first, followed by spinoidal dewetting, d) above the isotropic phase, strongly depends on the value of the extracted contact angle of the formed sessile droplets with temperature was found and e) on cooling, the value of the contact angle remained constant and the droplets remained until the re-crystalline phase was reached. Attempts to extract the values of the tension surface length were made using the modified Young equation. These values are monotonically decreased by increasing the temperature.

Conclusion: The surface of this FLC mixture was found stable by increasing the temperature within the SmC* and SmA phases. The dewetting was observed above the SmA –I phase transition temperature. These thin films are characterized by first order wetting transition.