scholarly journals Influence of Linking Group Orientation on Mesomorphism of Two Aromatic Ring Mesogens

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
L. K. Ong ◽  
S. T. Ha
Keyword(s):  
Isotropic Phase ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
Group Orientation ◽  
Heating And Cooling ◽  
Ester Linkage ◽  
Microscopy Techniques ◽  
Optical Polarizing Microscopy ◽  
Mesomorphic Properties ◽  
Dsc Thermograms

A new homologous series of alkyl 4-{[(4-chlorophenyl)imino]methyl}benzoates were prepared, and all the members are differentiate by the alkoxy chain length,CnH2n+1O, wheren=2–7, 9, 11, 13, 15. Their phase transition behaviors and mesophase characteristics were studied by differential scanning calorimetry (DSC) and optical polarizing microscopy techniques. DSC thermograms show direct isotropization and recrystallization during heating and cooling processes, respectively. The crystal phase changed directly to dark area textures (isotropic phase) without displaying any mesophase. The mesomorphic properties of compounds studied are strongly dependent on the orientation of the ester linkage. Reversed ester linkage has caused depression of mesomorphic property in the compounds studied.

scholarly journals Study of the Effects of Lateral Substitution (Bromo) on Mesomorphic Behaviours of Chalconyl Ester Derivatives

2016 ◽  
Vol 64 ◽  
pp. 135-143
Author(s):  
Ravindra Solanki ◽  
R.B. Patel
Keyword(s):  
Homologous Series ◽  
Present Series ◽  
Transition Curve ◽  
Melting Points ◽  
Polarizing Microscopy ◽  
Group Efficiency ◽  
Normal Manner ◽  
Crystal Properties ◽  
Optical Polarizing Microscopy ◽  
Mesomorphic Properties

Novel homologous series: RO-C6H4-COO-C6H3-Br-CO-CH=CH-C6H4-OC18H3(n) (ortho bromo to –COO-) is synthesized and studied with a view to understand and establish the relation between mesomorphic properties and the molecular structure with reference to lateral substitution of bromine (-Br) at middle phenyl ring. Chalconyl homologous series consists of thirteen between (C1to C18) homologues. Nematogenic mesomorphism commences from C5homologue and continue up to C18homologue in enantiotropic manner. Transition and melting points were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibited odd-even effect up to C8homologue. It (N-I) rises and fall with negligible deviations from its normal descending tendency which appears in case of homologues C10to C18. Thermal stability for nematic is 142.89 °C and the mesophase lengths vary minimum 8.0 °C to maximum 26.0 °C at the C7and C8homologue respectively. Liquid Crystal properties of present series are evaluated and compared with structurally analogous series and relative group efficiency order derived. Thus ,present series is predominantly nematogenic with absence of Smectic property. Analytical and spectral data supported moleculars of homologues.

Effects of Cyclic Heating and Cooling on the Banana-Phase Growing Behaviors of Banana-Shaped Liquid Crystal 1,3-Phenylene-bis[4-(4-octyl phenylimino)methyl]benzoate

2010 ◽  
Vol 428-429 ◽  
pp. 322-325 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Liquid Crystal ◽  
Nucleation And Growth ◽  
Methyl Benzoate ◽  
Isotropic Phase ◽  
Cyclic Heating ◽  
Phase Growth ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures

The effects of cyclic heating and cooling on the banana-phase growth behaviors of the prototype banana-shaped liquid crystal 1,3-phenylene-bis[4-(4-octylphenylimino)methyl]benzoate were investigated with differential scanning calorimetry and polarized optical microscopy, respectively. Cyclic heating and cooling can reduce the phase transition temperatures and increase the domain sizes of the banana phases of the banana-shaped liquid crystal. These results can be interpreted in terms of the nucleation and growth of the banana phases out of its isotropic phase of the banana-shaped liquid crystal.

Synthesis and Mesomorphic Properties of Three-Benzene-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(nonylcarboyloxyl) benzylideneamine]

2010 ◽  
Vol 428-429 ◽  
pp. 79-82 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Benzene Ring ◽  
Cyclic Heating ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures ◽  
Mesomorphic Properties

A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.

scholarly journals Synthesis and Mesomorphic Properties of New Fluorinated Schiff Base Liquid Crystals

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Sie-Tiong Ha ◽  
Teck-Leong Lee
Keyword(s):  
Schiff Base ◽  
Chemical Structure ◽  
Scanning Calorimetry ◽  
Smectic A ◽  
Related Series ◽  
Mesomorphic Property ◽  
Microscopy Techniques ◽  
New Compounds ◽  
Mesomorphic Properties ◽  
Base Liquid

Two new compounds, 4-alkanoyloxybenzylidene-4′-fluoroaniline and 4-fluorobenzylidene-4′-n-alkanoyloxyaniline comprising a terminal fluorosubstituent were studied. The fluoro substituent contributes to the molecular polarizability, thus affecting intermolecular interactions and hence resulting in smectic mesomorphism. The mesomorphic properties were studied using differential scanning calorimetry and polarizing optical microscopy techniques. The mesomorphic properties of compounds studied are strongly dependent on the orientation of the imine (CH=N) linkage. The former Schiff base exhibited smectic A phase whereas the latter compound did not display any mesophase. Reversed imine linkage has caused depression of mesomorphic property in the compound studied (4-fluorobenzylidene-4′-n-alkanoyloxyaniline). The mesomorphic properties of the present compounds were compared with other structurally related series to establish the chemical structure-mesomorphic property relationship.

scholarly journals Synthesis and Phase Transition Behaviours of New Chalcone Derivatives

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
S. T. Ha ◽  
Y. W. Low
Keyword(s):  
Phase Region ◽  
Spectroscopic Techniques ◽  
Organic Solution ◽  
Scanning Calorimetry ◽  
Chalcone Derivatives ◽  
Heating And Cooling ◽  
Phenyl Rings ◽  
Mesomorphic Property ◽  
Dsc Thermograms ◽  
C Nmr

A series of new chalcone derivatives with a general formula of C11H27COOC6H4COCH=CHC6H4X where X=F, Cl, Br, and NO2were well synthesized and crystallized from organic solution. The physical properties as well as the chemical formulations of these compounds were determined by spectroscopic techniques (FTIR, and1H and13C NMR). Differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) techniques were employed to study their transition temperatures and mesophase characteristics. DSC thermograms of compounds with fluoro and nitro substituents displayed direct isotropization and recrystallization during heating and cooling processes. Chloro and bromo analogues exhibited Cr1-to-Cr2transition within the crystal phase region. It was also found that enone linkage showed fewer tendencies to exhibit mesomorphic property compared to imine linkage. However, when enone linkage is combined with other central linkages and additional phenyl rings, it turns conducive to mesomorphism.

scholarly journals Liquid-crystalline heterodimesogens and ABA-heterotrimesogens comprising a bent 3,5-diphenyl-1,2,4-oxadiazole central unit

2012 ◽  
Vol 8 ◽  
pp. 472-485 ◽  
Author(s):  
Govindaswamy Shanker ◽  
Marko Prehm ◽  
Carsten Tschierske
Keyword(s):  
Liquid Crystalline ◽  
Optical Observations ◽  
Central Unit ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Polarizing Microscopy ◽  
X Ray ◽  
Nematic Phases ◽  
Lower Temperature ◽  
Optical Polarizing Microscopy

Three new types of terminally connected ABA-heterotrimesogens and heterodimesogens, composed of a bent 3,5-diphenyl-1,2,4-oxadiazole central unit and one or two rod-shaped 4-cyanobiphenyl cores or one 2-phenyl-1,3,4-thiadiazole core, connected by flexible spacers, have been synthesized, and their mesomorphic behavior was studied by optical polarizing microscopy (PM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All dimesogens exhibit broad ranges of cybotactic nematic phases (NcybA and NcybC), in some cases accompanied by additional mesophases (CybA or SmC) at lower temperature. The combination of the 3,5-diphenyl-1,2,4-oxadiazole unit with one cyanobiphenyl core leads to the removal of tilted smectic and cybotactic nematic phases (SmC, NcybC), which are replaced by the nontilted CybA phases and nematic phases composed of SmA-type clusters (NcybA). The orthogonal cybotactic nematic phases of bent-core mesogens are of special interest for achieving biaxial nematic phases of the orthorhombic type. The orthogonal (NcybA) and skewed (NcybC) cybotactic nematic phases were distinguished by XRD and optical observations.

Synthesis and Mesomorphic Properties of Three-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis(4-butoxybenzylideneamine)

2010 ◽  
Vol 428-429 ◽  
pp. 167-170
Author(s):  
Yuan Ming Huang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Optical Microscopy ◽  
Cyclic Heating ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Temperature Range ◽  
Heating And Cooling ◽  
Mesomorphic Properties

A three-ring containing bent-core compound 1,3-phenylene-bis(4-butoxybenzylidene amine) was synthesized and characterized with differential scanning calorimetry and polarized optical microscopy. It exhibited mesophases in the temperature range of 48-54oC for the first cyclic heating and cooling. Our results demonstrated that three-ring containing bent-core molecules can form mesophases.

scholarly journals pH-controlled synthesis of sustainable lauric acid/SiO2 phase change material for scalable thermal energy storage

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shafiq Ishak ◽  
Soumen Mandal ◽  
Han-Seung Lee ◽  
Jitendra Kumar Singh
Keyword(s):  
Electron Microscopy ◽  
Phase Change ◽  
Lauric Acid ◽  
Photoelectron Spectroscopy ◽  
Phase Change Materials ◽  
Precursor Solution ◽  
Thermal Reliability ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Heating And Cooling

AbstractLauric acid (LA) has been recommended as economic, eco-friendly, and commercially viable materials to be used as phase change materials (PCMs). Nevertheless, there is lack of optimized parameters to produce microencapsulated PCMs with good performance. In this study, different amounts of LA have been chosen as core materials while tetraethyl orthosilicate (TEOS) as the precursor solution to form silicon dioxide (SiO2) shell. The pH of precursor solution was kept at 2.5 for all composition of microencapsulated LA. The synthesized microencapsulated LA/SiO2 has been characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM). The SEM and TEM confirm the microencapsulation of LA with SiO2. Thermogravimetric analysis (TGA) revealed better thermal stability of microencapsulated LA/SiO2 compared to pure LA. PCM with 50% LA i.e. LAPC-6 exhibited the highest encapsulation efficiency (96.50%) and encapsulation ratio (96.15%) through Differential scanning calorimetry (DSC) as well as good thermal reliability even after 30th cycle of heating and cooling process.

Thermal properties of polybenzoxazine exhibiting improved toughness: Blending with cyclodextrin and its derivatives

2021 ◽  
pp. 095400832110130
Author(s):  
Hailong Li ◽  
Sipei Zhao ◽  
Li Pei ◽  
Zihe Qiao ◽  
Ding Han ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Hydrogen Bonds ◽  
High Performance ◽  
Practical Application ◽  
Scanning Calorimetry ◽  
Thermoset Resins ◽  
Chemical Structures ◽  
Microscopy Techniques ◽  
Fractured Surface ◽  
Scanning Electron

Polybenzoxazines are emerging as a class of high-performance thermoset polymers that can find their applications in various fields. However, its practical application is limited by its low toughness. The cyclic β-cyclodextrin and a newly synthesized derivative (β-cyclodextrin-MAH) were separately blended with benzoxazine to improve the toughness of polybenzoxazine. The results revealed that the maximum impact strength of the blend was 12.24 kJ·m−2 and 14.29 kJ·m−2 when 1 wt.% of β-Cyclodextrin and β-Cyclodextrin-MAH, respectively, were used. The strengths were 53% and 86% higher than that of pure polybenzoxazine. The curing reaction, possible chemical structures, and fractured surface were examined using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques to understand the mechanism of generation of toughness. The results revealed that the sea-island structure and the presence of hydrogen bonds between polybenzoxazine and β-cyclodextrin and β-cyclodextrin-MAH resulted in the generation of toughness. Furthermore, the curves generated during thermogravimetric analysis did not significantly change, revealing the good thermal properties of the system. The phase-separated structure and the hydrogen bonds present in the system can be exploited to prepare synergistically tough polybenzoxazine exhibiting excellent thermal properties. This can be a potential way of modifying the thermoset resins.

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