•A novel AIEE-active LLC possess three LC phases and high fluorescence quantum yield.•The in-plane electric field accompanying a rubbing alignment layer can induce the LLC molecules into ordered arrangement.•The well-aligned CN-NPFA film shows highly linearly polarized emission.•The field-induced LLC film has regular stripe profile.•It could advance LLC applications and prove helpful to future devices producing polarized luminescence.Luminescent liquid crystals (LLCs) have attracted significant interest for organic optoelectronic applications, especially for the generation of linear polarized light. Here, a novel LLC molecule, 2-(4-(nonanealkoxy)phenyl)-3-(4-formamidephenyl)-acrylonitrile (CN-NPFA), is reported, which shows strong fluorescence in the solid state due to the aggregation-induced enhanced emission (AIEE) effect. Moreover, a well-aligned liquid crystalline film using AIEE-active molecules, is obtained using an in-plane electric field with an alignment layer. It exhibits highly polarized luminescence (ρ = 0.74) with a high fluorescence quantum yield. The device is both cheap and easy to fabricate, and has the potential to be used in practical electro-optic applications.Download high-res image (401KB)Download full-size image

•A new optical switch based on AIE-active luminescent liquid crystals was developed.•The mixture material can emit partially linearly polarized light.•It is possibly to modulate photoluminescence intensity and its polarization.•It has the potential to be used in improved optical devices.We found reversible photo/thermal isomerization of the α-cyanostilbenic derivative (Z)-2-(4-aminophenyl)-3-(4-(dodecyloxy)phenyl)-acrylonitrile, (Z)-CN-APHP, which is accompanied by a large decrease in compatibility when mixed with a nematic liquid crystal. Moreover, a novel optical switch using a CN-APHP doped liquid crystal that emits partially linearly polarized light is investigated. By controlling the trans–cis isomerization of CN-APHP, it is possibly to modulate not only photoluminescence intensity but also its polarization. This could open possibilities to design improved optical devices.

The reflection bandwidth of cholesteric liquid crystals is typically on the order of 50–100 nm in the visible region. Static bandwidths greater than 100 nm can be observed in polymer stabilized cholesteric liquid crystals (PSCLCs) that possess a pitch gradient throughout the thickness of the cell. This work presents PSCLCs based on ionic polymer networks and chiral ions, which exhibit large reflection bandwidth tunability under a small applied direct current (DC) electric field. The reflection colors dynamically switch between white, orange, red and transparent. The underlying mechanism of the electrically controllable bandwidth in PSCLCs is the redistribution of the chiral ions under DC electric fields resulting in a pitch gradient variation along the optical axis. Removal of the electric field returns the PSCLC to its original optical properties due to the strong electronic attraction between the ionic polymer network and chiral ions. Moreover, the reflection bandwidth is also sensitive to the temperature.

•A tristable can be switched among the planar, focal conic and fingerprint states.•The mixture exhibits stable emission performance.•The photoluminescence can be controlled using an electric field.•It has the potential to be used in practical portable information systems.A tristable and electrically switchable optical switch based on luminescent molecule and cholesteric liquid crystal (CLC) is demonstrated. The CLC can be switched among the planar state, focal conic state and fingerprint state using the electric field. The interaction between the luminescent molecules and indium tin oxide substrate can be modulated by controlling the orientation of the luminescent molecules, which determine the stability of the three states. The optical property and fluorescent intensity of these states depend on the arrangement of liquid crystal molecules and all the three states can exist for several hours at room temperature without any observable change. Such a multi-stable electrical switch is simple to be fabricated, easy to be operated, and has low power consuming. It, therefore, has the potential to be used in practical portable information systems.

The reflection bandwidth of cholesteric liquid crystals is typically on the order of 50–100 nm in the visible region. Static bandwidths greater than 100 nm can be observed in polymer stabilized cholesteric liquid crystals (PSCLCs) that possess a pitch gradient throughout the thickness of the cell. This work presents PSCLCs based on ionic polymer networks and chiral ions, which exhibit large reflection bandwidth tunability under a small applied direct current (DC) electric field. The reflection colors dynamically switch between white, orange, red and transparent. The underlying mechanism of the electrically controllable bandwidth in PSCLCs is the redistribution of the chiral ions under DC electric fields resulting in a pitch gradient variation along the optical axis. Removal of the electric field returns the PSCLC to its original optical properties due to the strong electronic attraction between the ionic polymer network and chiral ions. Moreover, the reflection bandwidth is also sensitive to the temperature.