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This research introduces a novel liquid crystal molecular design approach based on the para-sexiphenyl (6P) structure. Six new liquid crystalline materials were synthesized, incorporating an alkyl terminal and lateral substitutions of the sexiphenyl core to achieve temperature-stable and broad nematic phases. The synthetic pathway involved cross-coupling, resulting in derivatives with strong nematogenic characteristics. Optical investigations demonstrated that the tested material had high birefringence values, making it promising for optical and electronic applications. These results open up new avenues of research and offer potential practical applications in electronics, photonics, optoelectronics and beyond. [ABSTRACT FROM AUTHOR]

The phase behaviour of the latest synthesised compound belonging to a family of (S)-4′-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-['m'-(2,2,3,3,4,4,4-heptafluorobutoxy) 'm'alkoxy]-benzoates (where 'm' means 3, 5 or 7 methylene groups) is described by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and Fourier-transform infrared absorption spectroscopy. It has been shown that as the length of the alkyl chain increases, a given liquid crystal possesses a greater number of mesophases and at a higher temperature it goes into the isotropic liquid phase. All examined compounds form a chiral smectic phase with antiferroelectric properties (SmCA* phase), in which the temperature range of occurrence increases with the length of the molecule. The number of methylene groups also affects the glass transition. The compound with the shortest alkyl chain ('m' = 3) is vitrified from the conformationally disordered crystal phase. For the compound with five -CH2- groups ('m' = 5), a glass transition from the monotropic high-order hexatic smectic SmXA* phase is observed. In the case of the liquid crystal with the longest carbon chain ('m' = 7), the vitrification from the less ordered SmCA* phase is visible. Differences in the crystallization kinetics, e.g., the nucleation-controlled mechanism for the compound with the shortest carbon chain vs. the complex phenomenon for its longer homologs, are discussed. [ABSTRACT FROM AUTHOR]

In this work, the synthesis of a new polysiloxane, poly {dimethylsiloxane-co-[4-(2,3-difluoro-4-hydroxyphenoxy) butyl] methylsiloxane} (dubbed PMFOS), is presented. This polymer exhibits high hydrogen bond acidity and was designed to be used as a sensor layer in gas sensors. The description of the synthetic route of the PMFOS has been divided into two main stages: the synthesis of the functional substituent 4-(but-3-en-1-yloxy)-2,3-difluorophenol, and the post-polymerization functionalization of the polysiloxane chain (methylhydrosiloxane-dimethylsiloxane copolymer) via hydrosilylation. The synthesized material was subjected to instrumental analysis, which confirmed its structure. The performed thermal analysis made it possible to determine some properties important for the sensor application, such as glass transition temperature and decomposition temperature. The results showed that PMFOS meets the requirements for materials intended for use in gas sensors based on acoustoelectric transducers. [ABSTRACT FROM AUTHOR]

Liquid crystals, compounds and mixtures with positive dielectric anisotropies are reviewed. The mesogenic properties and physical chemical properties (viscosity, birefringence, refractive indices, dielectric anisotropy and elastic constants) of compounds being cyano, fluoro, isothiocyanato derivatives of biphenyl, terphenyl, quaterphenyl, tolane, phenyl tolane, phenyl ethynyl tolane, and biphenyl tolane are compared. The question of how to obtain liquid crystal with a broad range of nematic phases is discussed in detail. Influence of lateral substituent of different kinds of mesogenic and physicochemical properties is presented (demonstrated). Examples of mixtures with birefringence Δn in the range of 0.2-0.5 are given. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of new deuterated liquid crystal (LC) compounds based on phenyl tolane core is described in this paper. The work presents an alternative molecular approach to the conventional LC design. Correlations between molecular structure and mesomorphic and optical properties for compounds which are alkyl-hydrogen terminated and alkyl-deuterium, have been drawn. The compounds are characterized by mass spectrometry (electron ionization) analysis and infrared spectroscopy. They show enantiotropic nematic behavior in a broad temperature range, confirmed by a polarizing thermomicroscopy and differential scanning calorimetry. Detailed synthetic procedures are attached. Synthesized compounds show a significantly reduced absorption in the near-infrared (NIR) and medium-wavelength infrared (MWIR) radiation range, and stand as promising components of medium to highly birefringent liquid crystalline mixtures. [ABSTRACT FROM AUTHOR]

Liquid crystal materials composed of mixed nematic compounds find broad use in liquid crystal displays and photonic applications. A ternary mixture formed from three different nematic compounds shows peculiar behavior such as tunable electro-optical properties dependent on the frequency of the driving voltage. The paper presents an analysis of the response time and phase retardation of a frequency tunable nematic liquid crystal mixture (under code name 5005). This material possesses high birefringence (Δn = 0.32 at 633 nm) as well as high dielectric anisotropy (Δε = 6.3 at 100 Hz). The unique property of the 5005 mixture is frequency-controlled phase modulation, as in a dual frequency liquid crystal, while dielectric anisotropy goes to zero instead of being negative at high frequencies. For each component of the mixture, details on mesomorphic properties and their role in the formulation of the mixture are reported. The 5005 mixture was characterized by multiple investigation techniques, such as temperature dependence dielectric anisotropy, transmittance measurements image polarizing microscopy, and UV stability. [ABSTRACT FROM AUTHOR]

Vibrational dynamics in the glass transition and the cold crystallization process of (S)-4′-(1-methyloctyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-benzoate (3F7HPhH7) was studied by Fourier transform infrared spectroscopy (FTIR) during cooling/heating experimental runs. The measured spectra processing was supported by quantum chemical density functional theory (DFT) calculations (frequency assignments). The perturbation-correlation moving window two-dimensional analysis (PCMW2D) was performed to examine how the height of individual absorption bands change under with temperature. Two-dimensional correlation analysis (2D-COS) was used to detect freezing-in or activation of the stochastic movements during the vitrification and the cold crystallization processes. Upon cooling, the vitrification process involves freezing-in of the stochastic movements of ester groups. Upon heating, as the cold crystallization process begins, the first to respond are the vibrations of the C–O–C and C=O groups in the rigid core. [ABSTRACT FROM AUTHOR]

Liquid crystals act on the amplitude and the phase of a wave front under applied electric fields. Ordinary LCs are known as field induced birefringence, thus both phase and amplitude modulation strongly depend on the voltage controllable molecular tilt. In this work we present electrooptical properties of novel liquid crystal (LC) mixture with frequency tunable capabilities from 100Hz to 10 KHz at constant applied voltage. The frequency tunability of presented mixtures shown here came from composition of three different families of rodlike liquid crystals. Dielectric measurements are reported for the compounds constituting frequency-controlled birefringence liquid crystal. Characterization protocols allowing the optimum classification of different components of this mixture, paying attention to all relevant parameters such as anisotropic polarizability, dielectric anisotropy, and dipole moment are presented. [ABSTRACT FROM AUTHOR]