Mesoporous chochleate particles doped liquid crystal as normally transparent smart window

Abstract

A composite layer of homogeneously aligned liquid crystal (LC) doped with nano or mesoporous microparticles (NMPs) has been shown to act as normally opaque smart window (SW) in what is called NMP-LC mode. The porosity of the particle plays two important roles: (i) When the LC infiltrates the particle, it brings its refractive index to be closer to that of its LC surrounding at a certain orientation of the LC molecules and creates a large index mismatch at the orthogonal orientation; (ii) the LC infiltration brings the porous particle density to be closer to the surrounding LC, thus preventing precipitation and floating. Here we demonstrate that LC doped with cochleate cigar-shaped hollow particles and using DMOAP as an alignment layer acts as a normally transparent smart window. Under voltage, the best scenario that explains the polarization-independent scattering is to have the cochleate particles inclined at an angle to balance the dielectric with the elastic forces effectively. The emergence of the scattering mode results from the symbiotic interplay of two distinct phenomena – the NMP effect and the electro-hydrodynamic instability effect. The synergy between these two effects manifests in lower operating voltage and frequency requirements for the device, hence less energy consumption. The scattering increases between 30 °C and 50 °C, thus it acts as a self-adjustable window giving more shade as the outside temperature rises. The threshold voltage is found to decrease with temperature. The SW exhibits high transparency in the OFF state, and high haze in the ON state, and the durability test shows that the SW switches for at least 6 days without degradation of optical contrast.