Electroconvection (EC) in liquid crystals (LCs) is extensively studied for the formation of regular nonequilibrium structures, and the applications that require strong light scattering and high haze. Doping the LCs with ionic species has proven to be an effective method to obtain uniform and high‐quality textures. Herein, zwitterion is explored as a new class of ionic dopant that has little problem of ion accumulation as compared to typical organic electrolytes. A rich variety of EC patterns are observed and characterized for both positive and negative LCs doped with a zwitterion Reichardt's dye. The initial homogeneous or homeotropic alignment, as well as the voltage and frequency of the applied electric field, is shown to influence the formation of EC patterns, among which the dynamic scattering mode (DSM) is specially examined for the application as privacy‐protecting smart windows. Using an LC mixture doped with zwitterions, the smart window demonstrates outstanding performance, as well as much improved durability for a wide range of operating conditions. Such a method offers a simple strategy for the fabrication of polymer‐free smart windows.
Polymer stabilized liquid crystal (PSLC) devices can be used as smart privacy windows that switch between transparent and opaque states. The polyimide alignment layer of a PSLC device is usually obtained by the treatment of polyamide acid (PAA) with temperatures over 200 °C. This hinders the fabrication of PSLC devices on flexible substrates, which melt at these high temperatures. In this work, the fabrication of a PSLC alignment layer using a lower temperature that is compatible with most flexible substrates, is demonstrated. It was found that the treatment of PAA at 150 °C could generate the same alignment for liquid crystals. Based on this, a PSLC device was successfully fabricated on a flexible polyethylene terephthalate (PET) substrate, demonstrating excellent electro-optic performances.
Nylon–cotton (NC) blend fabrics are widely used
in military
and industrial applications, but their high flammability still remains
a serious problem. In an effort to effectively and quickly impart
flame retardancy to the NC fabric, it was treated by simply blade
coating with a Cu2+-doped polyelectrolyte complex (CPEC)
that consists of ammonium polyphosphate (APP), polyethylenimine (PEI),
and copper sulfate. The viscosity of the CPEC can be adjusted by altering
the content of CuSO4, which controls the amount of extrinsic
and intrinsic ion pairs. By adjusting the proportion and content of
PEI, APP, and CuSO4, CPEC suitable for treating the NC
fabric was obtained. Only 0.067 wt % Cu2+ was needed to
adjust the viscosity and impart self-extinguishing behavior in a vertical
burning test. This simple two-step treatment provides a promising
technology to protect flammable polymeric substrates with ultralow
metal-doped polyelectrolyte complexes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.