Binary Mixtures of Hydrogen-Bonded Ferroelectric Liquid Crystals: Thermal Span Enhancement in Smectic X* Phase

2015 ◽  
Vol 70 (9) ◽  
pp. 757-774 ◽  
Author(s):  
Gopal Sangameswari ◽  
Nataraj Pongali Sathya Prabu ◽  
Mathukumalli Lakshmi Narayana Madhu Mohan
Keyword(s):  
Binary Mixtures ◽  
Thermal Equilibrium ◽  
Optical Microscope ◽  
Stability Factor ◽  
Benzoic Acids ◽  
Scanning Calorimetry ◽  
Ferroelectric Liquid Crystals ◽  
Binary Liquid ◽  
Smectic C ◽  
Hydrogen Bonded

AbstractThermotropic hydrogen-bonded ferroelectric binary liquid crystal mixtures comprising of N-carbamyl-l-glutamic acid (CGA) and p-n-alkyloxy benzoic acids (BAO) are investigated. Variation in the molar proportion of X and Y (where X=CGA+5BAO and Y=CGA+9BAO, CGA+10BAO, CGA+11BAO, and CGA+12BAO) comprising of four series yielded 36 binary mixtures. Optical and thermal properties of these mixtures are meticulously studied in the present article. In addition to the traditional phases, a novel smectic ordering namely smectic X* is observed in all the four series. The aim of the investigation is to obtain abundance occurrence of smectic X* with a large thermal span, and hence, the proportions of the binary mixtures are so chosen that the prelude task is accomplished. Optical tilt angle in smectic X* and smectic C* phases is experimentally determined, and a theoretical fit is performed. Phase diagrams of the four series are constructed from the data obtained from the differential scanning calorimetry and correlated with the phases recorded by the polarising optical microscope studies. Thermal stability factor and thermal equilibrium are also premeditated.

Design, Synthesis and Characterization of Hydrogen Bonded Binary Liquid Crystal Complex from 4-Methoxycinnamic Acid and 4-Hexyloxybenzoic Acid (4MCA:6OBA)

2017 ◽  
Vol 231 (11-12) ◽  
Author(s):  
Thamilarasan Ranjeeth Kumar ◽  
Sankaran Sundaram ◽  
Thangaiyan Chitravel ◽  
Ramasamy Jayaprakasam ◽  
Vellalapalayam Nallagounder Vijayakumar
Keyword(s):  
Liquid Crystal ◽  
Binary Mixture ◽  
Tilt Angle ◽  
Phase Variation ◽  
Optical Microscope ◽  
Scanning Calorimetry ◽  
Smectic C ◽  
Ir Studies ◽  
Methoxycinnamic Acid ◽  
Hydrogen Bonded

AbstractHydrogen bonded liquid crystal (HBLC) binary mixture has been synthesized from mesogenic 4-methoxycinnamic acid (4MCA) and mesogenic 4-hexyloxybenzoic acid (6OBA) with different mole ratio. The mesomorphic phase behavior and corresponding phase transition temperatures along with the enthalpy values were investigated by differential scanning calorimetry (DSC). The characteristic textures of 4MCA+6OBA binary mixture were observed by using polarizing optical microscope (POM). Fourier transform infrared spectroscopic (FT-IR) studies confirm the formation of hydrogen bond in the present binary mixture. A note worthy observation in this complex is that pure mesogens have no smectic phase where as 4MCA+6OBA binary mixture exhibits a nematic phase along with higher order smectic C (Sm C) phase. Variation of mole ratio influences thermal properties such as phase peak, enthalpy values and thermal span width of the present HBLC binary mixture complex. The optical tilt angle of 4MCA+6OBA for smectic C phase and thermal stability factors have been investigated. Optical tilt angle for smectic C phase is determined and same is fitted to a power law.

Observation of Induced Luminescence and Thermochromism in Achiral Hydrogen Bonded Liquid Crystal Complexes

2020 ◽  
Vol 234 (10) ◽  
pp. 1709-1733
Author(s):  
A. Ramya ◽  
V. Balasubramanian ◽  
R. Jayaprakasam ◽  
V. N. Vijayakumar
Keyword(s):  
Liquid Crystal ◽  
Nematic Phase ◽  
Density Functional ◽  
Atomic Charge ◽  
Optical Microscope ◽  
Band Gap Energy ◽  
Stability Factor ◽  
Scanning Calorimetry ◽  
Interesting Phenomenon ◽  
Hydrogen Bonded

AbstractA novel hydrogen bonded liquid crystal (HBLC) complexes are obtained from the non-mesogenic (benzylmalonic acid) and mesogenic (p-n-alkyloxybenzoic acid, where n = 6, 7 and 8) compound via intermolecular hydrogen bonds (H-bond). H-bonds are experimentally confirmed by the Fourier transform infrared spectroscopic (FT-IR) studies and the same is validated using density functional theory (DFT). Induced thermochromism is observed by the polarizing optical microscope (POM) and its possible applications are reported. Phase transition temperature and their analogous enthalpy values, stability factor and span width are determined by the differential scanning calorimetry (DSC) studies. Band gap energy is calculated using UV-visible and photoluminescence spectrum. Hyper conjugative stabilization energy and atomic charge distribution is studied by the natural bond orbital (NBO) studies. Mulliken analysis clearly reveals the intermolecular interaction and steric effect of the HBLC complexes. An interesting phenomenon is that the observation of luminescence and thermochromism in the highly fluidity nematic phase. This peculiar behavior is attributed due to the intermolecular H-bonding interaction between the BMA and nOBA compounds and the effect of rotatory motion of the molecules in nematic phase. Luminescence increases when the spacer moiety decreases in the present complexes is also reported. In nematic phase, the molecules are in different degrees of the excited state which is correlated with the hyper conjugative energy through NBO studies.

FORMATION OF CRYSTAL G PHASE IN HYDROGEN BONDED MESOGEN CONSTRUCTED BY p-n-ALKYL BENZOIC ACIDS WITH ORTHO-TOLUAMIDE

2009 ◽  
Vol 23 (14) ◽  
pp. 3187-3194 ◽  
Author(s):  
CH. RAVI SHANKAR KUMAR ◽  
S. SREEHARI SASTRY ◽  
T. MADHU MOHAN
Keyword(s):  
Benzoic Acid ◽  
Carbon Number ◽  
Acid Group ◽  
Optical Microscope ◽  
Benzoic Acids ◽  
Scanning Calorimetry ◽  
Polar Groups ◽  
Ft Ir ◽  
Non Covalent Interactions ◽  
Hydrogen Bonded

New supramolecular hydrogen bonded mesogens are designed with the non-covalent interactions between the two polar groups. Interesting observations made in the synthesis of new hydrogen bonded mesogen between the mesogenic group p-n-alkyl benzoic acid with n representing the alkyl carbon number from pentyl to decyl of benzoic acid group and non-mesogen ortho-toluamide containing nitro group. The thermodynamic properties of the observed textures are studied by polarizing optical microscope and compared with the corresponding differential scanning calorimetry. The results of hydrogen-bonded mesogen are studied in comparison with the free p-n-alkyl benzoic acids. The intermolecular hydrogen bonding between the two polar groups convinced by FT-IR favours the formation of hydrogen-bonded mesogen with crystal G phase different from their constituents.

scholarly journals Image Analysis Studies for Phase Transitions of Ferroelectric Liquid Crystals

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
S. Sreehari Sastry ◽  
B. Gowri Sankara Rao ◽  
K. B. Mahalakshmi ◽  
K. Mallika ◽  
C. Nageswara Rao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Image Analysis ◽  
Liquid Crystals ◽  
Optical Microscope ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Statistical Parameters ◽  
Ferroelectric Liquid Crystals ◽  
Phase Transition Temperatures ◽  
Parameter Values

Phase transition temperatures of ferroelectric liquid crystals ((S)-(-)-2-methylbutyl 4′-(4″-n-alkanoyloxybenzoyloxy) biphenyl-4-carboxylates (where n=16 and 18)) are studied through two techniques of image analysis. One is a statistical method, applied to compute the statistical parameters from the textures of each sample and the other, computation of Legendre moments being applied as image moment analysis, both of which are considered as a function of temperature. The textures of the samples are recorded with the polarizing optical microscope (POM) attached to the hot stage and high resolution camera. The phase transition temperatures of samples are inferred by the abrupt changes in the computed parameter values. The results obtained from the present methodology are in good agreement with those published in earlier literature done by the different techniques, like differential scanning calorimetry (DSC).

Supramolecular ferroelectric liquid crystals. Hydrogen-bonded complexes between benzoic acids and chiral stilbazoles

1996 ◽  
Vol 21 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Hideyuki Kihara ◽  
Takashi Kato ◽  
Toshiyuki Uryu ◽  
Seiji Ujiie ◽  
Uday Kumar ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Benzoic Acids ◽  
Ferroelectric Liquid Crystals ◽  
Bonded Complexes ◽  
Hydrogen Bonded

scholarly journals Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 223 ◽  
Author(s):  
Omaima A. Alhaddad ◽  
Hoda A. Ahmed ◽  
Mohamed Hagar ◽  
Gamal R. Saad ◽  
Khulood A. Abu Al-Ola ◽  
...  
Keyword(s):  
Binary Mixtures ◽  
Density Functional ◽  
Binary Systems ◽  
Uv Spectroscopy ◽  
Twist Angle ◽  
Optical Microscope ◽  
Geometrical Parameters ◽  
Scanning Calorimetry ◽  
Photophysical Studies ◽  
The Individual

Three binary systems were prepared by mixing of two different mesogenic derivatives, homologues, the first is azo/ester, namely 4-alkoxyphenylazo-4′-phenyl-4″-alkoxybenzoates (IIn+m) and the second is Schiff base/ester, namely 4-(arylideneamino)phenyl-4″-alkoxy benzoates (In+m). The two corresponding analogues from both series in the binary mixtures investigated are of the same terminal alkoxy chain length. Mesomorphic properties were investigated by differential scanning calorimetry (DSC) and phases identified by polarized optical microscope (POM). Photophysical studies were investigated by UV spectroscopy connected to a hot stage. Results were discussed based on constructed binary phase diagrams. All mixtures were found to exhibit eutectic compositions, with linear or slightly linear nematic and smectic A stability/composition dependences. Geometrical parameters were predicted applying density functional theory (DFT) calculations. Twist angle (θ), aspect ratio, dipole moment and the polarizability of the individual compounds were discussed and correlated with the experimental results to illustrate the enhanced the mesophase stability and the mesophase range of the mixture at the eutectic composition compared with those of their individual components.

scholarly journals New Homologues Series of Heterocyclic Schiff Base Ester: Synthesis and Characterization

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Yee-Ting Chong ◽  
Norazilawati Muhamad Sarih ◽  
Sie-Tiong Ha ◽  
Md. Rezaul Karim Sheikh
Keyword(s):  
Schiff Base ◽  
Relative Phase ◽  
Structural Information ◽  
Optical Microscope ◽  
Spectroscopic Techniques ◽  
Ester Synthesis ◽  
Scanning Calorimetry ◽  
Smectic C ◽  
Heating And Cooling ◽  
C Nmr

A homologous series of liquid crystal bearing with heterocyclic thiophene Schiff base ester with alkanoyloxy chain (CH3(CH2)nCOO–, where n=4, 6, 8, 10, 12, 14, 16) was successfully synthesized through the modification of some reported methods. The structural information of these compounds was isolated and characterized through some spectroscopic techniques, such as FTIR, 1H, and 13C NMR and elemental analysis. Textural observation was carried out using a polarizing optical microscope (POM) over heating and cooling cycles. It was found that all synthesized compounds (3a–g) exhibited an enantiotropic nematic phase upon the heating and cooling cycle with high thermal stability. Moreover, a characteristic bar transition texture was observed for compounds 3f and 3g which have shown transition of nematic-to-smectic C phase. This has been further confirmed by obtaining relative phase transition temperature using the differential scanning calorimetry (DSC).

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