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Frustrated phases in chiral liquid crystalline systems, such as the blue phase (BP) and the twist grain boundary (TGB) phase, can create new opportunities in liquid crystal research. These frustrated phases have unique optical properties which can be used for specific applications. A new binary mixture system composed of a chiral rod-like ferroelectric liquid crystal and an achiral hockey stick-shaped compound was designed. This binary system exhibits induced frustration, resulting in the emergence of the BP-III and TGBA* phases in addition to the chiral ferroelectric Smectic-C* phase. We report a comprehensive study on several binary mixtures (xH-22.5= 0.162, 0.25, 0.396, 0.562) designed of a chiral ferroelectric liquid crystal derived from the lactic acid, namely 4-(octyloxy)phenyl 3-methoxy-4-((4-((2-(pentyloxy)propanoyl)oxy)benzoyl)oxybenzoate and achiral hockey stick-shaped compound, namely (E)-4-((E-((3-(decyloxy)-2-methylphenyl)imino)methyl)-phenyl 3-(4-(dodecyloxy)phenyl)acrylate. These mixtures induced the blue phase (BP-III, ~2.5-6.2K) and the twist grain boundary Smectic-A*phase (TGBA* ~1.8-6K). Polarizing optical microscopy, birefringence, and dielectric spectroscopy were employed to investigate the BPIII and TGBA* phases, as those techniques provide insights into their structural and dynamic properties. The ferroelectric behaviour of the SmC* mesophase was investigated by electrooptics. The obtained results are discussed in relation to the molecular structures of the used materials. [ABSTRACT FROM AUTHOR]

In this work, we present the synthesis of two analogues of a lactic acid derivative selectively deuterated on phenyl and biphenyl moieties together with a detailed investigation of their properties within the Twist Grain Boundary smectic A* (TGBA*), the ferroelectric Smectic C* (SmC*) and the crystal E phases. The main structural features of the two liquid crystalline phases, namely TGBA* and SmC* phases, were determined by polarising optical microscopy, differential scanning calorimetry, electro-optical techniques, Small Angle X-ray Scattering (SAXS) and 2H Nuclear Magnetic Resonance (2H NMR) measurements. Preliminary results from Neutron Spin-Echo (NSE) spectroscopy, a technique rarely applied to study chiral liquid crystalline materials, are reported. The effect of the external magnetic field on the supramolecular structure of the ferroelectric phase was studied by means of 2H-NMR experiments under different external magnetic fields. The supramolecular and orientational ordering properties of this ferroelectric lactic acid derivative and its deuterated homologues are discussed in the frame of actual knowledge in the field of ferroelectric liquid crystal materials. [ABSTRACT FROM AUTHOR]

Self-assembling behaviour of a few lactic acid derivatives with several ester linkage groups in the molecular core has been studied. The molecular structure–physical property correlations has been discussed in the light of the temperature dependences of the static permittivity, dielectric anisotropy, spontaneous polarization, response time and torsional bulk viscosity for eight chiral ferroelectric liquid crystalline compounds. Depending on the molecular structure these compounds exhibit the chiral nematic (N*) phase, the paraelectric orthogonal smectic A* (SmA*) phase and the ferroelectric tilted smectic C*(SmC*) phase being thermally stable over relatively broad temperature range. The temperature behaviour of the spontaneous polarization clearly confirms the second order nature of the SmA*-SmC* phase transition and the first order nature of the N*-SmC* phase transition. The effect of temperature and molecular configuration on the polarization and on the dispersion anchoring energy coefficients has been established. The obtained results are discussed in order to contribute to the structure – property relationship for the specific class of soft organic materials which can be used for design of smart multifunctional liquid crystalline mixtures aimed for optoelectronic and photonic applications. • The structure–property correlations for eight chiral FLC's have been investigated. • The dielectric and electro optic properties have been reported. • Effect of molecular configuration on anchoring energy coefficients is established. • Low viscosity, large spontaneous polarization and low response times are observed. • The materials can be used for smart optoelectronic and photonic applications. [ABSTRACT FROM AUTHOR]

The tilted ferroelectric SmC* phase of three structurally different series having three aromatic rings in the core structure connected by ester groups with different end alkyl chain lengths, all of which are derived from lactic acid, have been observed by broadband dielectric spectroscopy. Introduction of structural variations within the liquid crystalline compounds has led to the formation of chiral nematic N*, or the paraelectric orthogonal SmA* phase at higher temperatures. The dielectric spectra strongly depend both on the temperature as well as the specific molecular structure of the self-assembling compounds possessing the ferroelectric polar order. The results reveal a strong Goldstone mode in the ferroelectric SmC* phase with ~kHz relaxation frequency. In the SmC* phase, the real and imaginary parts of the complex permittivity increase up to certain temperature near the SmC*-N*/SmA* transition and then decrease with increasing temperature, perhaps due to the disruption of the molecular domains at the onset of the SmA*/N* phase transition. The dielectric strength attains a maximum value in the SmC* phase and then decreases near the SmA*/N* phase transition. The dielectric strength is also influenced by the lengths of the alkyl chain and the nature of the connecting unit of the constituent molecules. The relaxation time and the relaxation frequency are found to vary with the molecular structure of the studied ferroelectric compounds.

In order to contribute to better understanding of the molecular structure–physical property relationship, properties of ferroelectric liquid crystalline materials derived from the lactic acid with the keto group in the molecular core have been studied. These compounds differing only by the length of the chiral and non-chiral alkyl chains exhibit the paraelectric SmA* and the ferroelectric SmC* phases over 150 K broad temperature range down to the room temperature. Temperature dependences of spontaneous polarization, tilt angle, layer spacing, helix pitch length and dielectric permittivity have been compared and discussed for all studied compounds. The effect of the alkyl chains length on mesomorphic properties has been established and discussed in comparison to that of similar materials. [ABSTRACT FROM PUBLISHER]

The tilted ferroelectric SmC* phase of three structurally different series having three aromatic rings in the core structure connected by ester groups with different end alkyl chain lengths, all of which are derived from lactic acid, have been observed by broadband dielectric spectroscopy. Introduction of structural variations within the liquid crystalline compounds has led to the formation of chiral nematic N*, or the paraelectric orthogonal SmA* phase at higher temperatures. The dielectric spectra strongly depend both on the temperature as well as the specific molecular structure of the self-assembling compounds possessing the ferroelectric polar order. The results reveal a strong Goldstone mode in the ferroelectric SmC* phase with ~kHz relaxation frequency. In the SmC* phase, the real and imaginary parts of the complex permittivity increase up to certain temperature near the SmC*-N*/SmA* transition and then decrease with increasing temperature, perhaps due to the disruption of the molecular domains at the onset of the SmA*/N* phase transition. The dielectric strength attains a maximum value in the SmC* phase and then decreases near the SmA*/N* phase transition. The dielectric strength is also influenced by the lengths of the alkyl chain and the nature of the connecting unit of the constituent molecules. The relaxation time and the relaxation frequency are found to vary with the molecular structure of the studied ferroelectric compounds. [ABSTRACT FROM AUTHOR]