Dependence of thermotropic mesomorphism on lateral nitro group

A novel homologous series RO-C₆H₄-COO-C₆H₃-(NO₂)-CO-CH?CH-C₆H₄OC₁₈H₃₇(n) para of chalconyl ester derivatives have been synthesized and studied with view to understanding the effect of an ortho substituted nitro group on thermotropic liquid crystal (LC) behavior. The novel homologous series consists of thirteen homologues (C₁ to C₁₈). The C₁ to C₄ homologues are nonliquid crystal (NLC) and the rest of the homologues (C₅ to C₁₈) homologues are enantiotropically nematogenic without exhibition of a smectic phase even in the monotropic condition. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Texture of nematic phase are threaded or Schlieren. Analytical, thermal and spectral data supported molecular structure of homologues. Thermal stability for nematic is 147.1°C whose mesophase lengths vary between 16.0 and 32.0°C the C₇ and C₁₈ homologues, respectively, and their mesogenic exhibition range between 96.0 and 166.0°C. Thus, the present novel series is middle ordered melting type, Group efficiency order is derived from comparative study of structurally similar series. The transition curves of a phase diagram behaved in normal manner except C₁₀ and C₁₆ homologues. Odd-even effect is observed for N-I transition curve. Group efficiency order derived is: -OC₁₂H₂₅ (n) > -OC₁₈H₃₇ (n) > -OC₁₈H₃₇ (n).     

Study of the mesomorphism of benzoates and cinnamates

Two ester homologous series of carboxy (-COO-) and ethylene-carboxy (-CH=CH-COO-) mesogens, viz. α-4-[4’-n-alkoxybenzoyloxy] phenyl β-4’’-methoxy benzoyl ethylenes (1) and α-4-[4’-n-alkoxy cinnamoyloxy phenyl β-4’’-methoxy benzoyl ethylenes (2)] are discussed. Series (1) and (2) differ at their central linking group. Mesophase are observed at four and five number members in both homologue series. Enantiotropic nematogenic property is observed in both series (1) and (2), while some smectic property is exhibited in series (2). Thermal stability of nematic-isotropic in series (1) is relatively low as compared to (2), smectogenic property is totally absent in series (2). In phase diagram, solid-nematic, solid-isotropic, and nematic-isotropic curve follow zigzag path rising and falling. Transition temperatures are observed through hot stage polarizing microscope. Analytical data supports the structure of molecules. Threaded, Schlieren-type textures of homologues are observed through microscope.     

Mesomorphism dependence of a terminal or lateral alkoxy group

A novel homologous series of thermotropic mesomorphs has been synthesized and studied with a view to understanding and establishing the effect of molecular structure on mesomorphic properties with reference to rigidity and flexibility of the homologues series: RO-C₆H₄-CH?CH-CO-C₆H₄-OC₁₈H₃₇(n). The novel homologous series comprises 13 novel homologues (C₁ to C₁₈), from which 11 homologues are enantiotropically mesogenic (C₃ to C₁₈). Smectogenic mesophase commences from C₇ homologue, and nematogenic mesophase is exhibited by C₃ to C₁₈ homologues in enantiotropic manner. Thus, C₇ to C₁₈ homologues are enantiotropically smectogenic plus nematogenic. Textures of smectic phase are of the type A or C, and that of nematic phase are threaded or Schlieren as confirmed through an optical polarizing microscope equipped with a heating stage. Transition curve of a phase diagram behaved in a normal manner except N-I transition curve, which shows minor deviating trend (C₁₂ to C₁₈) from expected normal behavior. An odd-even effect is exhibited by N-I and Sm-N transition curves. Analytical, spectral, and thermal data confirm the molecular structures of novel homologues. Thermal stabilities for smectic and nematic are 52.7°C and 66.6°C, respectively, whose total mesophase lengths range from 12.0°C to 28.0°C. Thus, novel series of chalcones is a low melting series whose mesogenic transition temperatures vary between 38.0 and 86.0°C.     

Study of Y-shaped liquid crystalline materials with polar nitro substituent

A new homologous series of Y-shaped liquid crystals namely 4-Nitro-[2′4′bis (4″-n-alkoxybenzoyloxy)] phenyl bisazobenzenes have been synthesized and its thermotropic properties studied on the hot stage of a polarizing microscope. The compounds consist four phenyl rings joined through ester and bisazo linkages with alkoxy and nitro as terminal substituents. The structures of synthesized compounds were confirmed by spectroscopic techniques such as FTIR, ¹HNMR as well as elemental analysis. The compounds were found to exhibit enantiotropic nematic and smectic mesophases. The role of molecular shape, size and polarity of functional groups in the mesophases formation is discussed.     

Study of mesomorphism dependence on molecular flexibility of an azoester series containing a napthyl unit

A novel azoester homologous series of liquid crystalline (LC) compounds: RO?C₆H₄-COO?C₁₀H₆-N:N-C₆H₄?OC₄H₉(n) without lateral substitution has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on thermotropic LC substances with reference to tailed-end group. The novel homologous series consists of 13 homologs (C₁ to C₁₈) whose nematogenic and smectogenic mesomorphism commences enantiotropically from C₆ and C₁₂ members of the series, respectively. The C₁₂–C₁₈ homologs are smectogenic and C₆–C₁₈ are nematogenic, of which C₁₂–C₁₈ homologs are smectogenic plus nematogenic. The C₁–C₅ homologs are nonmesogenic. Transition temperatures and the textures of the homologs were determined and identified by an optical polarizing microscope (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren and that of the smectic phase are of the type A or C. Transition curves Cr-M/I, Sm-N and N-I of a phase diagram behaved in normal manner except N-I transition temperature of C₁₀ homolog which deviated by 9°C–10°C from normal behavior. N-I transition curve exhibited odd-even effect. Analytical, spectral, and thermal data confirms the molecular structures of homologs. Thermal stability for smectic and nematic are 115.5°C and 138.5°C, respectively whose corresponding mesophaselengths are varied from 10.0°C to 16.0°C and 13.0°C to 24.0°C, respectively. Group efficiency order for smectic and nematic are derived from comparative study of structurally similar analogous series; as smectic: ?OC₄H₉ (n) > ?CH₃ > ?H; Nematic: ?H > ?OC₄H₉ (n) > ?CH₃     

The effect of position of octadecyloxy tail on the formation of liquid crystal with chalconyl-ester and chalconyl-vinyl ester series: Comparison with corresponding linkage group

Understanding of the electronic structures is indispensable for complete elucidation of the charge carrier behaviors in organic semiconductors. Although recent progress enabling accurate photoemission demonstrations of organic single crystals has greatly promoted such understanding, it had been achieved merely on partially oxidized surfaces by exposure to ambient conditions. In this study, we successfully prepared an oxide-free surface of the pentacene single crystal (PnSC) by cleavage in vacuum. X-ray and ultraviolet photoelectron spectroscopy measurements on the PnSC clean surface revealed improved energetic homogeneity of the C1s level and highest-occupied state in comparison to those of the partially oxidized surface.     

Dependence of mesomorphism on tail group in combination with a lateral methoxy group

A novel homologous series of esters with a lateral methoxy group and terminal n-heptyl cinnamate group was synthesized and studied to investigate mesomorphic behavior in relation to structure. The twelve membered series consists of methoxy to pentyloxy derivatives that are nonmesomorphic and the rest of the homologs as smectegenically mesomorphic, including C₆ and C₇ monotropic smectic and C₈ to C₁₆ enantiotropic smectic without exhibition of any nematic property. The textures of smectogenic mesophases are focal conic fan shaped or batonates of the type smectic-A or Schlieren-C. An odd-even effect is exhibited by the Sm–I transition curve in the phase diagram. The Cr–Sm and Sm-I transition curves behave in a normal manner. Transition temperatures and textures were determined on an optical polarizing microscope, equipped with a heating stage. Some representative members were characterized by IR, H¹NMR, mass spectra, and elemental analysis. Analytical data support the molecular structures of the homologs. Mesomorphic properties of the present novel series are compared with the structurally similar known series. The present series is smectogenic only, whose thermal average stability is 89.8^°C and of a middle-ordered melting type.     

Dependence of mesomorphism on geometrical shapes of isomeric and nonisomeric series of chalconyl esters

A meta substituted chalconyl ester homologous series: RO?C₆H₄?COO?C₆H₄(meta)?CO?CH?CH?C₆H₄?OC₁₂H_25(n)(para) is synthesized and studied with a view to understanding the effect of molecular substitution at meta position in a molecular structure on thermotropic liquid crystal properties. The novel homologous series consists of thirteen homologues (C₁ to C₁₈). All the homologues except the nonliquid crystal homologues C₁, C₂, C₃ are enantiotropic nematic with the absence of smectic properties. The transition and melting temperatures were determined by an optical polarizing microscopy (POM) equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren. Transition curves (Cr-N/I and N-I) behave in normal manner except homologues between C₁₀ and C₁₄ of N-I curve, which show negligible deviation from normal and a smooth descending tendency. The N-I transition curve exhibits an odd-even effect up to C₁₀ homologue and then the odd-even effect disappears for higher homologues. Analytical and the spectral data support the molecular structures. Thermal stability for nematic is 107.3°C and the mesophase lengths range between 13.0°C and 35.0°C at the C₁₈ and C₁₂ homologues respectively. Group efficiency order for nematic is derived on the basis of thermal stability as ?OC₁₂H_25(n) (linear) > ?OC₁₂H_25(n) (nonlinear) > ?OC₁₆H₃₃ (nonlinear).     

Molecular structural flexibility dependence of mesomorphism through ortho-substituted bromo group

A novel series of liquid crystal (LC) materials of Schiff's bases viz. RO-C₆H₄?CH?CH?COO?C₆H₄?N?CH?C₆H₄?Br (ortho) is synthesized and studied with a views to understanding and establishing the effect of molecular structure on liquid crystal properties and to provide novel thermotropic LC material to the scientific and technological community of research interest. The novel series consists of thirteen members (C₁ to C₈, C₁₀, C₁₂, C₁₄, C₁₆ &; C₁₈). All the members of a series are enantiotropic liquid crystals. Smectic (C₁₀?C₁₈) and nematic (C₁?C₁₈) property commence from C₁₀ and C₁ homologue respectively. Transition temperatures and the textures of homologues were determined using a polarizing optical microscope (POM) equipped with a heating stage. Transition curves Cr-M, Sm-N and N-I of a phase diagram behaved in normal manner. Odd–even effect is absent for Sm-N transition curve, but it is present for N-I curve. Sm-N transition curve is extrapolated to C₈ and C₆ nonsmectogenic homologues to determine and predict their latent ability for exhibition of smectic property. Analytical and spectral data confirms the molecular structures of homologues. Thermal stabilities of smectic and nematic are 85.4°C and 130.1°C °C whose upper and lower total mesophase length vary from 58.0°C to 06.0°C at the C₁₀ and C₁ = C₅ = C₆ homologue, respectively. Textures of nematic phase are threaded or Schlieren and smectic phase are of type A or C. LC properties of present novel series are compared with structurally series known series. Thus, present novel series is predominantly nematogenic and partly smectogenic with middle ordered melting type and considerable total mesophase length range.     

Synthesis and study of mesomorphic properties in rod-like chalconyl compounds

In order to investigate the influence of the central linking group and effect on flexibility on mesophase behavior of liquid crystal we have synthesized newly homologous series viz. 3-(4-Octyloxyphenyl)-1-(4′-n-alkoxy phenyl) prop-2-en-1-one (Series-l) consists of thirteen homologues (C₁ to C₈, C₁₀, C₁₂, C₁₄, C₁₆, C₁₈). Textures of a nematic phases are threaded or Schlieren type. The textures of smectic and nematic phase are directly judged from the heating and cooling condition. Group efficiency order for mesophases is derived on the basis of thermal stabilities from the comparative study of thermometric data determined from structurally analogous series. A transition curve as depicted in a phase diagram behaves in normal manner. Structural and conformational characterization of these new compounds had achieved by ¹H NMR, ¹³C NMR, IR, and elemental analysis.     

Mesomorphic properties of liquid crystalline compounds with chalconyl central linkage in two phenyl rings

In order to investigate the influence of the central linking group and the effect of flexibility on mesomorphism, we have synthesised a newly homologous series 3-(3-butoxyphenyl)-1-(4-n-alkoxy phenyl) prop-2-en-1-one (series-l) consisting of 13 homologues C₁–C₈, C₁₀, C₁₂, C₁₄, C₁₆ and C₁₈. In the present series, mesophase commences from the C₆ homologue. C₁–C₅ homologues did not exhibit liquid crystalline (LC) property, while C₆–C₁₂ homologues exhibited an enantiotropic nematic phase and the rest of the homologues C₁₄–C₁₈ displayed monotropic SmC and nematic mesophase. The transition temperatures of the synthesised compounds were determined by an optical polarising microscopy equipped with a heating stage. All newly synthesised compounds were confirmed by ¹H-NMR, ¹³C-NMR, IR and elemental analysis.     

Synthesis and characterization of rigid rode shape homologous series: Effect of tail iodo group

Arylpiperazine derivatives referred in this article possessed antitumor activity, which were synthesized and crystallized through the gradual evaporation process. The molecular structures of 2-(4-(2-(4-phenylpiperazin-1-yl)ethyl)benzyl)isoindoline-1,3-dione (C27H27N3O2, 1), 2-(4-(2-(4-(4-bromophenyl)piperazin-1-yl)ethyl)benzyl)isoindoline-1,3-dione (C27H26BrN3O2, 2) and 2-(4-(2-(4-(4-chlorophenyl)piperazin-1-yl)ethyl)benzyl)isoindoline-1,3-dione (C27H26ClN3O2, 3) were determi-ned and described. π-π interactions were observed in the packing modes of three compounds, and compound 2 and 3 showed halogen interactions between molecules nearby, which were different from compound 1. The dihedral angle values, the bond lengths, bond angles and the parameters demonstrated that involvement of halogen atoms did affect the conformation, configuration and cell parameter of the compounds.     

Role of n-alkoxy terminal end groups on mesomorphism

A homologous series RO-C₆H₄-CH:CH-COO-C₆H₄-CO-CH:CH-C₆H₄-OC₆H₁₃ (n) of novel liquid crystals (LC) has been synthesized and studied with a view to understanding and establishing the relation between molecular structure of a substance and the LC properties or behavior of thermotropic LC materials. Novel series consist of 11 homologues. C₁ and C₂ homologue derivatives are non-LCs and the rest of homologues (C₃ to C₁₆) are nematogenic without exhibition of smectic property. Transition temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curve Cr-N/I of a phase diagram behaved in normal manner. N/I transition curve partly deviated at C₆ and C₁₀ homologues from normal descending behavior, and exhibited very narrow and sharp odd-even effects. Textures of nematic phase are threaded or Schlieren. Thermal, analytical, and spectral data confirmed the molecular structures of novel chalconyl ester derivatives. Thermal stability for nematic is 95.77°C and the upper and lower mesophase lengths vary from 35 to 16°C at C₅ and C₈ homologues respectively. Group efficiency order derived for nematic on the basis thermal stability is -OC₁₀H₂₁ (n) > -OC₈H₁₇(n) > -OC₆H₁₃(n).     

Mesomorphism dependence on molecular rigidity and flexibility

A novel homologous series of mesogens was synthesized and studied with a view to understanding and establishing the relations between molecular structure and liquid crystal properties. Eleven members of the series were synthesized. Mesogenic behavior commences from the C₆ member and continues up to the C₁₄ member. The rest of the members, C₁ to C₅ and C₁₆, are non-mesogenic. Mesogenic homologues (C₆ to C₁₄) are enantiotropically nematogenic. Textures of nematic phase are threaded or Schlieren. Transition temperatures were determined by an optical polarizing microscope equipped with a heating stage. Analytical and structural data confirm the molecular structures of homologues. Thermal stability for nematic phase is 198.0°C. Mesomorphic phase length ranges from 11.0°C to 50.0°C. Cr-I/N and N-I transition curves of a phase diagram behave in normal manner from C₁ to C₁₂ members, and higher members C₁₄ and C₁₆ deviated from normal behavior. Mesogenic properties of present novel ester series are compared with the structurally similar series. Odd-even effect is missing for the N-I transition curve. Thus, the present series is partly nematogenic without exhibition of smectic property whose transition temperatures vary between 153°C and 210°C.     

Mesomorphism dependence on central bridge and tail ended polar group

Abstract

Severe operation conditions in the agriculture industry and numerous influencing factors complicate the selection of a contact material for switching devices. Attempts have been made to change the Ag-CdO contact material to a less toxic one. Environmentally friendly copper-base contact materials have been created for devices, which operate in agricultural electric systems, meanwhile being low-cost and with pre-set level of reliability in terms of transient resistance.     

Synthesis and Evaluation of Liquid Crystal Behavior of a Novel Homologous Series: 4-(4′-n-Alkoxy benzoyloxy) Phenylazo-2″, 6″-dimethylbenzenes

A novel homologous series entitled 4-(4′-n-alkoxy benzoyloxy) phenyl azo 2^″, 6^″-dimethyl benzenes consisting of 12 members is reported. Liquid crystal behavior as a nematogenic mesophase commences from the pentyloxy homologue monotropically and then continues enantiotropically until the last hexadecyloxy homologue without exhibition of any smectogenic behavior. An odd-even effect is observed for nematic-isotropic transition curve of the phase diagram. The textures of the nematic mesophase are of the threaded or Schlieren type. Analytical and spectral data support the molecular structure of the homologues. Transition temperatures of the novel homologues were determined by an optical polarizing microscopy. Liquid crystal properties of a novel homologous series are compared with other known homologous series. The average thermal stability for the nematic phase is 77.1°C.     

The Mesogenic Behavior of Isomeric and Nonisomeric Series of Novel Azoesters. 4-(4′-n-Alkoxy Benzoyloxy) Phenylazo-2″-Bromobenzenes

A novel homologous series: 4-(4′-n-alkoxy benzoyloxy) phenylazo-2^″-bromobenzenes is synthesized and studied with a view to understanding and establishing the effects of molecular structure on mesogenic behavior in a series. The mesogenic property commences from fifth homologue to the last homologue. The transition temperatures of the series are relatively low ranging between 68°C and 143°C. The mesogenic range varies between 6°C and 22°C. The novel azoester series is nematogenic without exhibition of any smectogenic property and an average thermal stability of 89.4°C. The mesogenic behavior of the novel series is compared with structurally similar isomeric/nonisomeric other known series.