Direct Observation of Polymer-Stabilized Blue Phase I Structure with Confocal Laser Scanning Microscope

Direct Observation of Polymer-Stabilized Blue Phase I Structure with Confocal Laser Scanning Microscop

Exploring the Impact of Linkage Structure in Ferroelectric Nematic and Smectic Liquid Crystals

The liquid crystal molecule 3-fluoro-4-(3,4,5-trifluorophenyl)phenyl 2,6-difluoro-4-(trans-5-n-propyl-1,3-dioxane-2-yl)benzoate (DIO) has attracted considerable interest owing to its unique ferroelectric nematic phase and extraordinarily high dielectric constant. To expand the DIO series, novel analogs with 1,3-dioxane units converted to ester units (EST analogs) were synthesized, and their physical properties were characterized. The EST analogs exhibited ferroelectric phases similar to those of the corresponding DIO analogs. Interestingly, an EST analogue featuring a defluorinated benzoate unit exhibited a ferroelectric smectic A phase, despite its smaller longitudinal dipole moment of 6.9 D. This result diverges from the common knowledge that the formation of large longitudinal dipoles is traditionally effective in the emergence of ferroelectric phases. Unlike the DIO series, the EST analogs can be readily obtained without the formation of undesired geometric isomers, which is advantageous for practical applications. The results of this study provide valuable insights into the design of liquid-crystalline materials expressing ferroelectric phases

Stabilizer-Concentration Effects on the Size of Gold Submicrometer-Sized Spherical Particles Prepared Using Laser-Induced Agglomeration and Melting of Colloidal Nanoparticles

Pulsed laser melting in liquids (LMLs), a convenient method of submicrometer-sized spherical particle (SMP) preparation, induces nanoparticle (NP) melting and fusion using laser irradiation at a moderate fluence for colloidal NPs. Our earlier study, conducted to produce gold SMPs (AuSMPs) from gold NPs (AuNPs) stabilized by sodium carbonate, demonstrated that the AuSMP size increased concomitantly with decreasing stabilizer concentration, although it has been suggested that laser fluence fundamentally determines the SMP size. This study elucidates an explanation of this phenomenon. Results obtained through experimentation showed the same relation when LML was conducted using AuNPs stabilized by sodium citrate. The narrower size distribution (65 ± 4 nm) of AuNPs used in this study than that of AuNPs used in earlier studies enabled us to ascertain that AuNPs smaller than the source AuNPs (approximately 10 nm diameter) are generated during laser irradiation via AuNP evaporation that occurs simultaneously with the AuNP agglomeration. A theoretical calculation predicts that the temperature increased by laser heating of AuNP depends strongly on the AuNP size, suggesting that efficiencies of stabilizer removal and agglomeration of the 10 nm AuNPs are lower than those of the source 60 nm AuNPs. For that reason, 10 nm AuNPs are likely to remain at high stabilizer concentration, leading to the formation of smaller AuSMPs because of insufficient growth. We also confirmed that such a mechanism (AuNP-size-dependent agglomeration efficiency) is applicable to improve the growth efficiency of AuSMPs on LML using AuNPs prepared by laser ablation in liquids with a wide size distribution. When smaller AuNPs were removed from the colloids by centrifugation, the amount of AuNPs remaining after LML decreased and larger AuSMPs were formed

Short chiral pitch and blue phase stability in cholesteric liquid crystal mixtures by adding achiral benzoic acid derivative

Cholesteric liquid crystal (CLC) is anticipated to have applications such as blue light and ultraviolet (UV) light blocking for human skin owing to its selective wavelength reflection against incident sunlight through several hundred nanometres of a periodic helical twist structure. In this study, we investigated short chiral pitch control and enlargement of the blue phase (BP) temperature range by adding an achiral constituent of 4-n-octylbenzoic acid (8 BA) into CLC mixtures composed of three kinds of cholesteryl compounds: cholesteryl chloride, cholesteryl pelargonate and cholesteryl palmitate. Hydrogen bonding dependence of chiral pitch and BP temperature range were also investigated for achiral dopant (8 BA) and CLC mixture through temperature-dependent Fourier-transform infrared analysis. It was found that 40 wt% of 8 BA within the CLC mixture selectively reflected UV and blue light over 360–400 nm with a decrease of chiral pitch. It was also found that the BP temperature range increased by 15.6°C owing to hydrogen bond dimers composed of 8 BA molecules in the CLC mixture.</p