Controlled pattering of surface micro-droplets via micellization of Polymeric Amphiphiles in liquid crystalline fluids

Abstract

In this work, we report a simple and versatile approach to pattern microdroplets of liquid crystals (LCs) encapsulated by polymeric amphiphiles on substrates. When the thermal trigger is introduced into a LC layer confined between two bounding plates coated with Poly (octadecyl methacrylate) (PODMA), we observed PODMA to diffuse into the LCs and form micro-sized droplets onto the substrates upon cooling. The size and density of droplets are precisely controllable by the tail length of PODMA, heating temperature, and rate of temperature change. We demonstrate the formation of surface droplets to be associated with the micellization of PODMA in LCs. The thermal trigger (increase in temperature) facilitates the desorption of coated PODMAs from substrates and the diffusion of them into LCs. The subsequent decrease in temperature reduces the critical micelle concentration of PODMA, thus resulting in the formation of birefringent quasi-2D hemisphere droplet. In addition, we found the internal configuration of LCs and the morphology of droplets to be controllable via anchoring energy, roughness, and waviness of bounding plates. This work was supported by the NRF (2021R1A4A1030944 and NRF-2021R1A2C2095010).