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Micro-sized chiral-nematic liquid crystal (N* LC) polymer particles have attracted considerable interest as versatile reflective colorants with selective circularly polarized light (CPL) properties. However, challenges in achieving the desired size distribution of N* LC particles have led to an incomplete understanding of their reflective characteristics. In this study, we successfully synthesized N* LC particles via dispersion polymerization, enabling precise control over size polydispersity by manipulating the composition of the polymerization solvent. Our investigation revealed that monodisperse N* LC particles displayed distinct reflection bands with high CPL selectivity, while polydisperse particles exhibited broader reflection with lower CPL selectivity. These findings underscore the potential to synthesize N* LC particles with tailored reflective properties using identical monomeric compounds. Furthermore, we demonstrated the production of multifunctional reflective colorants by blending N* LC particles with varying reflection colors. These discoveries hold significant promise for advancing the development of reflective colorants and anti-counterfeiting printing techniques utilizing micro-sized N* LC particles. [ABSTRACT FROM AUTHOR]

The luminescence of materials in condensed phases is affected by not only their molecular structures but also their aggregated structures. In this study, we designed new liquid-crystalline luminescent materials based on biphenylacetylene with a bulky trimethylsilyl terminal group and a flexible alkoxy chain. The luminescence properties of the prepared materials were evaluated, with a particular focus on the effects of phase transitions, which cause changes in the aggregated structures. The length of the flexible chain had no effect on the luminescence in solution. However, in crystals, the luminescence spectral shape depended on the chain length because varying the chain length altered the crystal structure. Interestingly, negative thermal quenching of the luminescence from these materials was observed in condensed phases, with the isotropic phase obtained at high temperatures exhibiting a considerable increase in luminescence intensity. This thermal enhancement of the luminescence suggests that the less- or nonemissive aggregates formed in crystals are dissociated in the isotropic phase. These findings can contribute toward the development of new material design concepts for useful luminescent materials at high temperatures. [ABSTRACT FROM AUTHOR]

Formation of gratings by means of the photoinduced alignment change of polymer liquid crystals (PLCs) has been explored in a glassy state. To obtain high diffraction efficiency (η), we synthesized highly birefringent PLCs containing an azobenzene group directly connected with a tolane moiety (3ATm), in which the alkyl spacer length (CH[sub 2])[sub m] was varied as m=6, 9 and 12. It was found that the values of birefringence in all the PLCs were about 0.4. The behaviors of the photoinduced alignment change and the formation of gratings were found to be dependent on the alkyl spacer length of 3ATm. [ABSTRACT FROM AUTHOR]

Photoinduced alignment in a polymer liquid crystal prepared from 6-{1-[4-(2-cyano-4-nitrophenylazo)phenyl]piperazino}hexyl acrylate and 4'-[6-(methacryloyloxy)hexyloxy]-4-cyanobiphenyl was investigated for the first time on irradiation with a polarized He-Ne laser beam at 633 nm. The azobenzene moieties as well as the inert cyanobiphenyl mesogenic units were aligned with the molecular long axis perpendicular to the polarization direction of the irradiation light. Alignment induced on short irradiation was reversible, while that induced under prolonged irradiation was irreversible due to the occurrence of crosslinking which might be caused by photoinduced decomposition of the azobenzene moieties during the photoirradiation process. [ABSTRACT FROM AUTHOR]

Pure organic luminescent materials with high efficiency in the solid state are of great importance for potential applications. Unlike blending two or three dyes, getting white-light emission from a single component is a hot research topic for its advantages in practical applications. Although thermo/mechanochromic materials are a smart class of stimuli-responsive systems, using these materials to manipulate the luminescence spectrum to achieve full-color emission from one component is rarely reported. In this work, we have designed two novel liquid crystal copolymers containing different monomer ratios of ethynylbiphenyl and biphenylcarbonitrile skeletons in the side chains. The polymers are free of rare or precious metals and exhibited thermochromism, mechanochromism, white emission from a single component, and high emission efficiency in the solid state. Ethynylbiphenyl skeleton is the key structure as a luminescent group that emits white light upon heating to the liquid crystal phase. However, controlling the ratio between ethynylbiphenyl and biphenylcarbonitrile side chains is essential to get high emission efficiency along with good purity of the white luminescence. The thermochromism and mechanochromism primarily due to the transition between creating and breaking down π-π interactions with different modes of molecular packing. This transition switches the emission color from blue to white (thermochromism) and vice versa (mechanochromism). The developed polymers showed a smart stimuli-responsive behavior and provided a simple strategy to get single-component white-light luminescent materials in the solid state. • We designed smart stimuli-responsive copolymers with numerous merits: • Simple structure, pure organic, liquid crystallinity, and strong emission in the solid state. • Color tuning by a combination of luminescence thermo- and mechanochromism. • White emission from a single chromophore upon heating to the liquid crystal phase. • Phenylacetylene skeleton is a key structure to switch the emission color upon heating. [ABSTRACT FROM AUTHOR]

This research focuses on the characterization of a simple organic molecule incorporating biphenyl, methacrylate, trimethylsilyl acetylene, and liquid crystal compounds. Extensive analysis of the molecule's physical and optical properties, including refractive index, extinction coefficient, dielectric constant, and conductivity, was conducted. Complementary TD-DFT computations validated the experimental findings. The molecule exhibited intriguing behavior in terms of extinction coefficient and refractive index, showing an initial increase followed by a decrease with increasing photon energy. CASTEP/DFT simulations confirmed these results. The molecule demonstrated surfactant properties, indicated by its increasing dielectric constant and optical conductivity, suggesting enhanced charge transfer and energy storage potential. Additionally, the study investigated the impact of flexible spacer length on organic compounds, revealing that shorter spacers improve refractive index, extinction coefficient, and optical conductivity, indicating enhanced light absorption and bending capabilities. The observed differences in optical values between compounds with different spacer lengths can be attributed to factors such as molecular packing, dipole moment, molecular orientation, and light interactions. Furthermore, the removal of the TMS group from the main compound impacted the optical properties by influencing molecular arrangement, electronic states, and energy levels. These findings provide valuable insights for the design of materials with tailored optical properties. • A simple organic molecule combined four different groups, each with its potential optical applications. • The results revealed a significant resemblance between the DFT simulated and observed values. • The dielectric constant behavior indicates the surfactant properties of this material. • The optical conductivity pattern provides additional evidence for the surfactant properties. • The flexible spacer length has a direct impact on the optical properties. [ABSTRACT FROM AUTHOR]

The article presents a systematic study of nematic-isotropic phase transition of azobenzene liquid-crystalline polymers (LCPs) that demonstrates an efficient change in birefringence. A new molecular architecture was proposed to induce a large change in birefringence upon irradiation of light. LCP that contains a longer azotolane moiety was also developed based from the idea above.

Luminescent coatings have several exciting applications. Polymers have been reported as both corrosion inhibitors and luminescent materials. Mild steel corrosion is a major economic problem. Moreover, full-color luminescence from one material is a hot research topic due to the advantages of such materials. Here, some liquid crystal polymers (LCPs) have been checked as corrosion inhibitors of mild steel in an acidic medium (1.0 M H 2 SO 4) through potentiodynamic polarization techniques. The LCPs showed high anticorrosion efficiency depending on their structure. These LCPs were confirmed as mixed-type inhibitors. Furthermore, the studied LCPs have aggregation-induced emission behavior with controlled emission colors (blue, white, and green) via adjusting the solution concentration. The molecular aggregation changed according to the solution concentration, and thus the relative emission intensity was tuned at different wavelengths of the visible range. Interestingly, moderate solution concentrations displayed white emission from a single component. The LCPs also exhibited a stable emission behavior at high temperatures. Because these materials combine the advantages of polymers, LCs, corrosion inhibitors, and white-light emitters, these current findings should open a door to develop more attractive luminescent coatings. [Display omitted] • Some liquid crystal polymers (LCPs) have been studied as luminescent coatings. • White emission from a single material was obtained. • The luminescence color was tuned by adjusting the solution concentration. • The studied polymers showed high anticorrosion efficiency. [ABSTRACT FROM AUTHOR]