Synthesis and Phase Behaviors of New Heterocyclic Liquid Crystals: Nematic and Smectic Properties

2014 ◽  
Vol 699 ◽  
pp. 233-238 ◽  
Author(s):  
Kok Leei Foo ◽  
Sie Tiong Ha
Keyword(s):  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Phase Behaviour ◽  
Scanning Calorimetry ◽  
Smectic A ◽  
Lower Member ◽  
Smectic A Phase ◽  
Phase Behaviors ◽  
New Compounds ◽  
Mesomorphic Properties

A series of new rod-shaped liquid crystal, 6-methoxy-2-(4-alkyloxybenzylidenamino) benzothiazoles possessingeven numbers of carbon atoms at the alkyloxy chain (CnH2n+1O-, n = 10, 12, 14, 16, 18) are prepared and characterized. The phase behaviour of these new compounds was studied by differential scanning calorimetry and polarising optical microscopy. All members exhibited mesophase. Influence of alkyl chain length on the mesomorphic properties was studied. Enantiotropic nematic phase was identified in all the members except for n = 18. Lower member (n = 10) exhibited monotropic (metastable) smectic A phase. The enantiotropic smectic A phase was observed fromn-dodecyloxy derivatives onward to the last homologous synthesized.

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.

Miscibility Studies Indicating a Low Temperature Smectic A Phase in Biaromatic Liquid Crystals with Re-entrant Behaviour

1981 ◽  
Vol 36 (11) ◽  
pp. 1201-1204
Author(s):  
A. Göbl-Wunsch ◽  
G. Heppke ◽  
R. Hopf
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Chain Length ◽  
Nematic Phase ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Smectic A ◽  
Smectic A Phase ◽  
Miscibility Studies

Recent reports [1] have shown that compounds of the homologous series of the 4(4-n-alkyloxy- benzoyloxy)-4′-cyanoazobenzenes (Cn; n = 1 - 12), all have a low temperature smectic A phase (SA″). The homologues with alkyl chain length n≧9 exhibit in addition a high temperature smectic A phase (SA′), separated from the first one by a re-entrant nematic phase (N(re)). Homol­ogues of this series were used for miscibility studies with some compounds of the biaromatic liquid crystal series of the 4-cyano-4′-n-alkyloxybiphenyls (n̄ CBP) and of the 4-cyanobenzylidene- 4′-n-alkyloxyanilines (CN · n̄). The phase diagrams studied show that the smectic A phases of biaromatic liquid crystalline nitrile compounds correspond to the high temperature smectic SA′ type and are not miscible with the low temperature SA″ phase. Moreover, the shapes of the transition temperature curves to the SA″ phase indicate a low temperature smectic A phase (SA″) for the biaromatic compounds. This suggests that for biaromatic compounds with re-entrant behaviour, the dependence of liquid crystalline phase sequences on the alkyl chain length is very similar to that of triaromatic compounds.

scholarly journals Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

2009 ◽  
Vol 5 ◽  
Author(s):  
Gundula F Starkulla ◽  
Elisabeth Kapatsina ◽  
Angelika Baro ◽  
Frank Giesselmann ◽  
Stefan Tussetschläger ◽  
...  
Keyword(s):  
Terminal Group ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Maximum Phase ◽  
X Ray ◽  
Smectic A ◽  
Polar Groups ◽  
Chain Lengths ◽  
Mesomorphic Properties ◽  
Phase Width

Based on 5-(4-hydroxyphenyl)-2-octylpyrimidine 8, 5-phenylpyrimidine derivatives 3–7, 9 with different spacer chain lengths (C2 up to C6) and different terminal polar groups (Br, Cl, N3, OH, CN) were synthesized by etherification and nucleophilic substitution. The mesomorphic behaviour of these compounds was investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (WAXS and SAXS) and revealed smectic A mesophases for bromides, chlorides and azides 3, 4 and 6. For these compounds a maximum phase width was observed for the C5 spacer regardless of the terminal group, whereas the hydroxy- and cyano-substituted derivatives 5 and 7, respectively, were non mesomorphic and showed only melting transitions.

The effect of the alkyl chain length on the mesomorphic properties of new lactic acid derivatives

2014 ◽  
Vol 41 (8) ◽  
pp. 1179-1187 ◽  
Author(s):  
Miroslav Kašpar ◽  
Věra Hamplová ◽  
Vladimíra Novotná ◽  
Oliva Pacherová
Keyword(s):  
Lactic Acid ◽  
Chain Length ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Mesomorphic Properties

Synthesis and Mesomorphic Properties of New Liquid Crystalline Cyclohexyl-phenyl- and Dicyclohexyl-pyrimidines

1979 ◽  
Vol 34 (11) ◽  
pp. 1535-1541 ◽  
Author(s):  
Alois Villiger ◽  
Arthur Boiler ◽  
Martin Schadt
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Viscosity Reduction ◽  
Refractive Indices ◽  
Thermal Compatibility ◽  
Chain Lengths ◽  
New Compounds ◽  
Mesomorphic Properties ◽  
End Group

Abstract Liquid Crystals, Cyclohexyl-phenyl-pyrimidines, Dicyclohexyl-pyrimidines The synthesis and mesomorphic properties of three new classes of cyano-substituted cyclohexyl-phenyl-and dicyclohexyl-pyrimidines are reported. The compounds are colourless, chemically and photochemically stable and have wide nematic mesophases. The thermal compatibility of the new compounds with other nematic liquid crystals is excellent. The large static positive dielectric anisotropics are shown to depend strongly on the position and number of hydrogenated rings as well as on the alkyl chain lengths within a homologous series. The reported bulk viscosities vary considerably among homologues. Hydrogenating the ring adjacent to the cyano end group causes η to increase, whereas a considerable viscosity reduction compared to nonhydrogenated homologues was found by hydrogenating the ring adjacent to the alkyl end group. The measured refractive indices of the new compounds are comparable to those of biphenyls.

The Effect of Terminal Alkyl Chain Length on Mesomorphic Properties of 4-Alkoxyphenyl-4'-Alkylbenzoates

1980 ◽  
Vol 59 (3-4) ◽  
pp. 253-272 ◽  
Author(s):  
Mary E. Neubert ◽  
L. T. Carlino ◽  
D. L. Fishel ◽  
R. M. D'sidocky
Keyword(s):  
Chain Length ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Mesomorphic Properties

scholarly journals Effect of Alkyl Chain Length in Anions on the Physicochemical Properties of Cellulose-Dissolving Protic Ionic Liquids

2019 ◽  
Vol 72 (2) ◽  
pp. 55 ◽  
Author(s):  
Hideki Hanabusa ◽  
Yuko Takeoka ◽  
Masahiro Rikukawa ◽  
Masahiro Yoshizawa-Fujita
Keyword(s):  
Physicochemical Properties ◽  
Chain Length ◽  
Alkyl Chain ◽  
Ionic Conductivities ◽  
Alkyl Chain Length ◽  
Cellulose Dissolution ◽  
Protic Ionic Liquids ◽  
Scanning Calorimetry ◽  
Protic Ionic Liquid ◽  
Chemical Structures

A protic ionic liquid (PIL) composed of 1,8-diazabicyclo[5.4.0]-undec-7-ene (DBU) and acetic acid can dissolve cellulose under mild conditions and catalyse its transesterification. To investigate the relationship between physicochemical properties and chemical structures, PILs composed of DBU and carboxylic acids with varying alkyl chain lengths were prepared as cellulose-dissolving solvents. The thermal behaviours of the PILs were analysed by thermogravimetry and differential scanning calorimetry, and their viscosities, ionic conductivities, and cellulose-dissolution abilities were determined. The effect of the alkyl chain length in the carboxylate ion on the physicochemical properties of the PILs was investigated. With increasing chain length, the thermal stability and ionic conductivity increased, whereas the melting point (Tm), glass-transition temperature (Tg), cellulose solubility, and viscosity decreased. The cellulose solubility increased as the difference between the pKa values of the DBU and carboxylic acid (ΔpKa) increased. In addition, the cellulose solubility increased with the increasing density of the PIL. It was revealed that PILs with a high ΔpKa value and a carboxylate ion with a short alkyl chain are suitable for cellulose dissolution.

Modification of traditional benzoxazine by blending with polyfunctional benzoxazines containing aromatic group and fluorene group

2020 ◽  
pp. 095400832097408
Author(s):  
Ting Wang ◽  
Zhi-yi Guo ◽  
Jun-yi Wang ◽  
Abdul Qadeer Dayo ◽  
Wen-bin Liu ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Cross Section ◽  
Alkyl Chain ◽  
Mechanical Analysis ◽  
Alkyl Chain Length ◽  
Curing Process ◽  
Scanning Calorimetry ◽  
Crosslinking Degree ◽  
Good Catalytic Activity ◽  
The Cross

A series of polyfunctional benzoxazine monomers containing aromatic and fluorene group (AMFB) were used as modified agents to improve the performance of typical bifunctional bisphenol-A-aniline-based (BA-a) benzoxazine resins. The polymerization behaviors of BA-a/AMFB blends were investigated by using the differential scanning calorimetry (DSC), while the dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were used to analyze the thermomechanical and thermal properties of BA-a/AMFB copolymers [poly(BA-a/AMFB)]. Moreover, the cross-section morphologies of poly(BA-a/AMFB) were observed by scanning electron microscope (SEM). The experimental results showed that BA-a monomer has good catalytic activity for AMFB monomers during the curing process. Compared with BA-a polymer [poly(BA-a)], due to the introduction of heat-resistant fluorene ring and the increase of the crosslinking degree of copolymers, the copolymers showed higher glass transition temperature and better thermal properties. For poly(BA-a/AMFB), the T 5, T 10, and Y c were higher than those of poly(BA-a). With the increase of the alkyl chain length of AMFB monomers, the cross-section creases gradually changed from linear to dendritic, and the number of creases increased significantly, which indicated that the toughness of the copolymers was significantly improved.

Key Factors to Prepare Polyelectrolytes Showing Temperature-Sensitive Lower Critical Solution Temperature-type Phase Transitions in Water

2012 ◽  
Vol 65 (1) ◽  
pp. 91 ◽  
Author(s):  
Yuki Kohno ◽  
Hiroyuki Ohno
Keyword(s):  
Phase Transition ◽  
Lower Critical Solution Temperature ◽  
Alkyl Chain ◽  
Alkyl Chain Length ◽  
Phase Behaviour ◽  
Solution Temperature ◽  
Temperature Sensitive ◽  
Key Factors ◽  
Critical Solution Temperature ◽  
Type Phase

Tetrabutylphosphonium styrenesulfonate and its homopolymer showed a lower critical solution temperature-type phase transition in water. As the hydrophobicity of these monomeric and polymeric salts affects phase behaviour, the phase transition temperature of the polyelectrolyte was changed by the introduction of monomers having different alkyl chain length on the phosphonium cations.

Sign in / Sign up

Export Citation Format

Share Document