In this study, we demonstrate a novel method for fabricating polymer stabilized cholesteric liquid crystal (PSCLC) films with non-uniform pitch distribution by utilizing two kinds of photo-induced processes. Based on the large HTP temperature dependence of a chiral dopant, polymer networks were formed at two distant temperature points in sequence. The influence of the polymerization conditions on the reflectance properties of PSCLCs before and after polymerization was investigated. The results strongly suggest that the location and bandwidth of the reflection band can be controlled preferably by adjusting the ultraviolet light intensity and irradiation time of UV-light. In addition, the morphology of the polymer network in the composites was studied using scanning electron microscopy (SEM). A general correlation between polymerization conditions, the network morphology, and the reflective region will be outlined.

•Three non-planar TPA-based n-type polymers were firstly designed and synthesized.•The physicochemical properties of polymers were tuned via molecular engineering.•The best performance for TPA-based solar cells can be reached 2.17%.Constructing non-planar conjugated systems is important to achieve high performing acceptors for non-fullerene solar cells. Non-planar unit triphenylamine (TPA) was copolymerized with accepting units, isoindigo (IIG) or naphthalene diimide (NDI), to afford three non-planar conjugated polymers. By changing the accepting moieties and the alkyl chains, the physicochemical properties and photovoltaic characteristics of the conjugated polymers were systematically tuned. As a result, the efficiency of the all-polymer solar cells was significantly enhanced to 2.2%.Download high-res image (235KB)Download full-size image

PDLC films were prepared by polymerization-induced phase separation (PIPS) method along with varying composition ratio between curable epoxy monomers/poly-oxy-propylene-di-amine (POPDA) cross-linking agent/Class α, longitudinal nematic liquid crystal (LC) linear chain polymer mixtures and their optical and pristine morphological properties have been analyzed to investigate their suitability as aligned nematic phase of LC. The refractive index of isotropic cross-linked polymer network could be influenced by the relative content of curable monomers structure PPGDE ~380 and PPGDE ~640 which increased the LC droplet size with POPDA. Meanwhile, it is examined that the decreasing of peel strength and transmittance of all the samples decrease of wavelength in the wavelength range of 300–800 nm due to the lower cross-linking density of the polymer network with effect of strongly influenced by the alkoxy (R-O) and flexible chain length of curable monomers, which also affect the electro-optical properties and droplet size of LC in PDLC films. Our results demonstrate that the LC droplet size of the isotropic cross-linked polymer network could be regulated by adjusting the monomers structure, composition ratio, relative wt% of POPDA, PPGDE ~380 and PPGDE ~640; then aligned nematic phase of LC have the optical properties of uniaxial crystals and their potential applications for PDLC smart glass market and display fields.

Polymer dispersed liquid crystal (PDLC) films were prepared by polymerization-induced phase separation method with nematic LC content as low as 40 wt%, and the electro-optical properties were carefully investigated. To accomplish this, the structure of multi-functional curable epoxy monomers with different composition feed ratios and the weight percentages of the two groups were examined in this study. The combined effects of heat-curable monomers’ structure on the conspicuous morphology of polymer network of PDLC films formed small holes and suitably distributed coin-like networks in both groups A and B, respectively. The detailed characteristics and morphology of polymer network of PDLC films were analyzed by employing liquid crystal device parameter tester, UV-Vis-NIR spectrophotometer and scanning electron microscope. Meanwhile, the enhanced curing temperature effects on the alkyl chain length, short flexible chain length, and rigid chain segment containing epoxy monomers structure on the increasing morphology of polymer network as well as electro-optical properties of PDLC films were also studied. It was found that the LC domain size of the polymer network could be regulated by adjusting the structure and composition ratio of curable epoxy monomers, and then the electro-optics of the PDLC films could be optimized, which is beneficial for decreasing the total LC content in PDLC devices.

Polymer dispersed liquid crystal (PDLC) films were formed by thermal polymerisation-induced phase separation in epoxy monomer/polyamine/liquid crystal (LC) mixtures. The effects of the epoxy monomer functionality on the morphology of polymer network, electro-optical and peel strength of PDLC films were studied. As the functionality of epoxy monomer increased, the LC domain size of PDLC films decreased resulting in higher threshold voltage and saturation voltage, longer rise time, shorter decay time, meanwhile the peel strength of PDLC films enhanced.

A series of novel side-chain cholesteric liquid-crystalline elastomers based on polysiloxane and cholesterol derivate monomer were prepared by adopting a crosslinking agent containing binaphthalene group. The chemical structures and mesomorphic properties of the monomers and elastomers were confirmed by FT-IR, 1H NMR, DSC and POM measurements. Worthily, the elastomers exhibited unusual temperature dependence of the helical twisting power (HTP) which is demonstrated resulting from coordination of the crosslinking agent and the mesogenic units. With increase in temperature, the HTP of elastomers containing small quantity of the crosslinking unit exhibited a turning point, while that of elastomers comprising much more crosslinking unit shifted straight. Furthermore, a single layer wide-band reflective film with non-uniform pitch distribution was prepared by utilizing the HTP variety of elastomers with change in temperature. From scanning electron microscopy (SEM) investigations, the mechanism of the broadband reflection was verified.

In this study, we demonstrate a novel method for fabricating polymer stabilized cholesteric liquid crystal (PSCLC) films with non-uniform pitch distribution by utilizing two kinds of photo-induced processes. Based on the large HTP temperature dependence of a chiral dopant, polymer networks were formed at two distant temperature points in sequence. The influence of the polymerization conditions on the reflectance properties of PSCLCs before and after polymerization was investigated. The results strongly suggest that the location and bandwidth of the reflection band can be controlled preferably by adjusting the ultraviolet light intensity and irradiation time of UV-light. In addition, the morphology of the polymer network in the composites was studied using scanning electron microscopy (SEM). A general correlation between polymerization conditions, the network morphology, and the reflective region will be outlined.