Effect of Network Concentration on the Performance of Polymer-Stabilized Cholesteric Liquid Crystals with a Double-Handed Circularly Polarized Light Reflection Band

Abstract

Polymer-stabilized cholesteric liquid crystals (PSCLCs) with a double-handed circularly polarized reflection band are fabricated by a wash-out/refill method. By removing the low molar weight LCs from the original PSCLC film, desirable liquid crystals (LCs) can be infiltrated into a prefabricated polymer network. The results showed that the memory of the polymer network controls the resulting material properties. The concentration of the prefabricated polymer network also plays a relevant role in the formation of a singlelayer cholesteric LC (Ch-LC) structure that has a clear-cut double-handed circularly polarized reflection band. A light-scattering phenomenon occurring in the system alters the reflection properties of Ch-LCs, which is due to the weak anchoring effect of the network when PSCLC film contains a low network concentration. Both kinds of circularly polarized reflection become more obvious with increase in the network concentration, followed by the strong anchoring effect of the network. The technique developed in this study has great applications in industries that require solid optical functional films and coatings.

Photo-Thermal Modulation of Cholesteric Liquid Crystals with a Dual Circularly Polarized Light Reflection Band

“…Similarly with that of our previous study [21][22][23][24][25][26], a polymer template with a RHHS was achieved by photo-polymerizing C6M monomers in PSCLCs which initially defined the periodicity or pitch (P) of the structure, then subsequently removed the nonreactive LCs from the system as shown in Fig. 2(b).…”

“…Within the bandwidth, light with the same handedness as that of the Ch-LCs will be circularly reflected, while the component with opposite handedness will be circularly transmitted [12,13]. Also the helical structure of Ch-LC is extremely sensitive to external influences such as temperature, pressure, and electric field and to the chemical modification of the molecules [14][15][16][17][18][19][20][21][22][23][24][25][26].…”

“…The polymer template from the PSCLCs was formed by photopolymerizing LC monomers that were dispersed within a Ch-LC mixture, which initially defined the handedness and periodicity of the helical structure and then was subsequently removed as mentioned in our previous studies [21][22][23][24][25][26]. Herein, based on the memory effect of the polymer template and the photo/thermo responsive characteristics of the GCLCO with AD were introduced into the Ch-LCs system.…”

Dye induced great enhancement of broadband reflection from polymer stabilized cholesteric liquid crystals

“…A wash‐out/refill method has also been utilized to evaluate that the network structure gradient existed in the films, since the polymer network has a characteristic of memorizing Ch‐LC helix structure in PSCLCs when the concentration of diacrylate monomers reaches a certain value 34, 35. The mixture V was prepared with weight ratio of C6M/DCM/S811/Dye/Irg651/TEB30B = 5.0/10.0/11.0/1.2%/0.5%/72.3% as shown in Table 1.…”

Effects of polymer network on electrically induced reflection band broadening of cholesteric liquid crystals

“…This type of polymer stabilized CLCs have been used to make a variety of optical devices such as displays, high‐efficiency filters, and smart windows . In these devices, the polymer network produces a pitch gradient or a non‐uniform pitch distribution with thermal or optical stimuli, template, and micro‐gel blending . The reflection bandwidth therein is often fixed and cannot be electrically modulated significantly.…”