Mesophase Textures Research Articles

Investigation of Phase States, Thermo-Morphologic, Magneto-Morphologic and Refractive Properties of Mesophases in Dodecyltrimethyl Ammonium Bromide – Water Lyotropic Liquid Crystalline System

Abstract We report the phase states in dodecyltrimethyl ammonium bromide/water (DDTMABr–H2O) lyotropic liquid crystalline system. The temperature-concentration phase diagram of this system has been determined. Isotropic micellar L1 phase, nematic-calamitic NC and hexagonal E mesophases have been observed in DDTMABr/H2O system. Dynamics of transformations of magnetically induced textures in NC and E mesophases has been investigated. Temperature and concentration dependences of the refractive index in the L1 phase, NC and E mesophases have been determined. The appearance of the magnetically induced aligned textures of NC mesophase and changes of the optical birefringence vs. time have been investigated.

Enhanced liquid crystal properties in symmetric ethers containing the oxazepine core: synthesis and characterization of seven member heterocyclic dimers

Four new series of symmetric dimers derived from the basic heterocyclic oxazepine core were designed, synthesized, characterized and investigated for liquid crystal properties. The chemical structures of the prepared molecules were characterized by infrared, 1H/13C nuclear magnetic resonance spectra and elemental analysis. Thermal properties and mesophase textures were evaluated by using a combination of differential scanning calorimetry and polarized optical microscopy techniques. Most of the compounds exhibited monotropic liquid crystalline phases in cooling processes. The effect of the spacer chain length and terminal alkoxy chain were studied for the influence on the type of mesophase formed by the homologous series of compounds. Lower members possessing the methylene spacer and a terminal alkoxy-chain favoured smectogenic properties; those derived from medium methylene spacer with terminal alkoxy chain favoured nematogenic properties whereas molecules derived with a higher methylene spacer with terminal alkoxy chain members did not favour any liquid crystalline properties.

Molecular flexibility dependence mesomorphism

ABSTRACTA novel series of chalconyl homologue derivatives with RO.C6H4.COO.C6H4.CO.CH:CH-C6H4.N.(CH3)2 (Para) have been synthesized and thermotropically studied with a view to understanding and establishing the effect of molecular structure on mesomorphic behavior of the novel homologues. The series consists of thirteen homologues (C1 to C18). C7 to C18 homologues are smectogenic, C4 to C18 nematogenic and C1 to C3 nonmesomorphic. Thus, novel chalconyl series is predominantly nematogenic and partly smectogenic. Transition temperatures and textures of mesophases were determined using an polarizing optical microscope (POM) equipped with a heating stage. Analytical and spectral data confirmed molecular structures of homologues. Phase transition curves showing phase behavior in a phase diagram behaved in normal manner. Thermal stability for smectic and nematic are relatively low at 59.6 °C and 76.6 °C respectively whose, smectogenic and nematogenic phase length vary from 12 to 16 °C and 06 to 20 °C, respectively. Mesomorphic behaviors of the present series are compared with a structurally similar known homologous series.

Mesomorphism dependence on molecular flexibility

ABSTRACTA novel ester homologous series of liquid crystals with a highly polar laterally substituted –OCH3 group is synthesized and studied with a view to understanding and establishing the effects of molecular structure involving lateral substitution on liquid crystal behavior. The novel series RO·C6H4·COO·C6H3·OCH3(ortho)CH=CH·COO·C2H5 consists of 12 homologs of which C7, C8, C10 are nematogenic and C12, C14, C16 homologs are smectogenic. The rest of the homologs are nonliquid crystals. The textures of nematic phase are threaded and the smectic phase is of the type A or C. Transition temperatures and the textures of mesophases were determined by an optical polarizing microscope equipped with a heating stage. Analytical and spectral data support the molecular structures. The N-I and Sm-I transition curves behave in normal manner without exhibition of an odd-even effect. Average thermal stability for smectic and nematic are 127.3°C and 129°C, respectively. The total mesophase length ranges from 17°C to 57°C and series is of a middle ordered melting type with transition temperatures varying between 82°C and 148°C. The liquid crystal properties of present novel series are compared with, structurally similar known homologous series.

Mesomorphism Dependence of Chalconyl Derivatives on Position of -CH=CH- Unit

ABSTRACTA novel homologous series of heterocyclic chalconyl esters (C1 to C16) has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties and the degree of liquid crystallinity. The C1 to C6 homologues are not liquid crystals, the C7 homologue is enantiotropic nematic, the C8 to C16 homologues are smectogenic in addition to nematogenic (C8 & C10 monotropic smectic). The texture of nematic phases are threaded or Schlieren and that of the smectic phase are fan-shaped smectic-A or smectic-C type. Transition temperatures and the textures of mesophases were determined by an optical polarizing microscope equipped with a heating stage. Transition curves Cr-I/M, Sm-N/N-Sm, and N-I showing phase behaviors of series in a phase diagram behave in normal manner. Thermal stability for smectic and nematic are 115.66°C and 126.83°C and their mesophase lengths minimum to maximum are 6.3 to 12.9°C and 6.9°C to 17.4°C, respectively. Analytical and spectral data confirms the molecular structures of homologues. LC properties of present novel series are compared with structurally similar other reported series.

Mesomorphic dependence on molecular rigidity by central bridge and homo–hetero ring systems

ABSTRACTA novel homologous series of thermotropic derivatives containing a heterocyclic ring was synthesized and studied with a view to understanding and establishing a relation between liquid crystal (LC) properties and the molecular structure of chalconyl derivative in general. The series comprises 12 homologues, of which smectogenic LC property commences from the decyloxy (C10) homologue and continues for C12, C14, and C16 homologues. Homologues C1 to C8 are non-liquid crystals. Exhibition of nematogenic mesophase is totally absent. Transition and melting temperatures were determined by an optical polarizing microscope equipped with a heating stage. Spectral and analytical data confirmed the molecular structures of homologues. The textures of smectic mesophase are A or C, and are determined by a miscibility method. The average thermal stability of the smectic phase is 113.57°C. The mesogenic phase length ranges between 4.1°C and 11.1°C. Thus, it is a middle-ordered melting-type series of shorter range of liquid crystallinity with absence of nematogenic character. Some LC properties of the present series are compared with a structurally similar known homologous series.

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

ABSTRACTA 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.

Synthesis of novel azoester homologous series of liquid crystalline behavior and the study of mesomorphism dependence on lateral substitution of middle phenyl ring

ABSTRACTThe titled azoester liquid crystalline homologous series consists of eleven homologues. The pentyl to tetradecyl derivatives of the series are nematogenic without exhibition of smectogenic character. Rest of the members of the series are nonliquid crystalline in nature. Textures of the nematic mesophase are schlieren or threaded type. Transition curves in the phase diagram showed normal phase behavior. Transition temperatures and liquid crystal behavior observed under an optical polarizing microscope equipped with a heating stage. An odd even effect is observed for nematic-isotropic transition curve. Analytical and spectral data confirms the structures of the molecules. Present homologous series is predominant nematogenic and partly nonmesogenic. Average thermal stability for nematic is 125.33°C and nematogenic mesophase length varies between 12°C to 48°C at tetradecyl (C14) and octyl (C8) derivatives, respectively.

Mesomorphism dependence on lateral substitution and central bridge

ABSTRACTA novel ester homologous series was synthesized and studied with a view to understanding and establishing the effects of molecular structure on liquid crystal properties with a common laterally substituted –OCH3 group and changing terminal groups. The novel series consists of twelve members. The C1 to C3 members are not liquid crystals and the rest of the members C4 to C16 are smectogenic without exhibition of nematic character. Textures of smectic phase are focal conic fan shaped of the type A or C. The transition temperatures and textures of smectic mesophases were observed through hot stage polarizing microscopy (POM). The transition curves (Cr-I or Cr-M and Sm-I) behaved in normal manner. Analytical and spectral data support the molecular structures. Average thermal stability for smectic is 77.25°C and smectogenic mesophase ranges from 15°C to 33°C. Liquid crystal properties of the present series are compared with structurally similar homologous series. Thus, the series is smectogenic only with three homologs nonmesogenic.

Synthesis and Study of Novel Mesogenic Homologous Series: 4-(4′-n-alkoxy benzoyloxy)-n-propyl Cinnamates

A novel homologous series of liquid crystals viz. 4-(4′-n-alkoxy benzoyloxy) n-propyl cinnamates comprising of 11 homologues has been synthesized. It is a middle ordered melting type of series with exhibition of smectic and nematic mesophases. The first to fifth members of the series are non-mesomorphic. Mesomorphic behavior commences from the sixth homologue. The octyloxy (C8) and decyloxy (C10) homologues are polymesomorphic. The smectic–nematic and nematic–isotropic transition curves behave in a normal manner except for the hexadecyl derivative, which slightly deviates from normal behavior (N–I). An odd–even effect was not observed for the N–I or Sm–N transition curves. The texture of nematic phase is threaded or Schlieren and that of the smectic phase is focal conic fan shaped of the smectic-A type. Transition temperatures and textures of mesophases were observed through an optical polarizing microscope equipped with a heating stage. Thermal stability and mesomorphic characteristics are compared with a structurally related series. Analytical and spectral data support the structure of the molecules.

Dependence of Mesomorphism on Terminal End Group of a Molecule

A novel azoester homologous series of liquid crystals consisting of 12 members is majorly nematogenic without the exhibition of smectic mesomorphism, except for the hexadecyloxy derivative. The methoxy and ethoxy members are monotropically nematic and the rest of the homologs are enantiotropically nematogenic. Transition temperatures and mesophase morphology were determined on an optical polarizing microscope equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type. Infra red, 1H NMR, mass spectral data, and elemental analysis data confirm the molecular structures of the novel homologs. The mesophase length varies from 00 to 72°C and the average thermal stability for the nematic phase is 133.5°C. Liquid crystal properties vary from homolog to homolog in present novel series. The liquid crystal behavior of the presently investigated novel series is compared with structurally similar known series. The transition curves (Cr-N/Cr-I and N-I/I-N) behave in a normal manner. The N-I/I-N transition curve exhibit an odd-even effect. The series is majorly nematogenic without exhibition of smectogenic character. Only the C16 homolog is nonmesogenic.

Mesomorphism Dependence on Terminally Substituted End Group

A novel homologous series of liquid crystalline substances has been synthesized and studied with a view to understanding and establishing the relation between liquid crystal properties and molecular structure. The novel ester series consists of eleven enantiotropically smectogenic homologous without exhibition of nematogenic property. Transition temperatures were determined with an optical polarizing microscope equipped with a heating stage. Textures of smectic mesophase are focal conic fan shaped of smectic A or C type. Analytical and spectral data confirms the molecular structures of homologous. Transition curve, Cr-Sm behaved in normal manner. Transition curve Sm-I behaved in a normal manner up to the octyloxy (C8) homolog derivative and then behaved in the unusual manner for the C10, C12, C14, and C16 derivatives. An odd-even effect is observed for the Sm-I transition curve. The series entirely smectogenic with a middle-ordered melting type and a moderate mesophase length. The average thermal stability for smectic is 128.09°C and mesophase length ranges from 8.6°C to 73.2°C. The mesomorphic (LC) behavior of the novel series is compared with structurally similar known homologous series.

Synthesis and Study of Molecular Structure and Its Relation to Liquid Crystal Behavior in a Novel Azoester Series

A novel liquid crystal (LC) homologous series of 12 azoesters was synthesized and evaluated, and nine members of the series exhibited enantiotropically or monotropically nematogenic LC behavior. Smectogenic character is totally absent. The methoxy, tetradecyloxy, and hexadecyloxy homologues are non-liquid crystals (NLC). Textures of nematic phase are threaded, or schlieren. The solid–isotropic/nematic and N-I or vice versa transition curves behave in normal manner. The N-I transition curve exhibits an odd-even effect. The average thermal stability for nematic is 113.25°C. Mesomorphic phase length ranges from 21 to 35°C. The textures of nematic mesophase and transition temperatures were determined by an optical polarizing microscope equipped with a heating stage. Analytical and spectral data confirm the molecular structures of homologues. The LC behavior of the present novel series is compared with a structurally similar known series. The present series is predominantly nematogenic with the absence of smectic property, and is of a middle-ordered melting type.

Mesomorphism Dependence on Terminal/Lateral Substitution of Nonlinear Azoester Molecules

A novel azo ester homologous series of liquid crystals (LCs) 2(4′-n-alkoxy benzoyloxy) napthyl 1 azo-3″ nitrobenzenes consists of eleven members of a series with enantiotropic nematogenic mesophase formation and without exhibition of smectogenic property by all the eleven homologs. The nematogenic mesophase textures are threaded or Schlieren. Solid-nematic and nematic-isotropic transition curves of the phase diagram behave in normal manner except for the decyloxy, dodecyloxy, and tetradecyloxy homologs. Analytical and spectral data confirm the molecular structures of homologues. Thermal stability for the nematic phase is 132.6°C, and the degree of mesomorphism varies between 34°C and 79°C and the series if of a middle-ordered melting type. An odd-even effect is observed for the N-I transition curve with alternation of transition temperatures. The LC behavior of the series is compared with other structurally similar known homologous series to establish the relation between mesomorphism and molecular structure.

Comparative investigations of the thermotropic and optical refractive properties in micellar isotropic phase and nematic-calamitic mesophase of hexadecyltrimethyl ammonium bromide/water and hexadecyltrimethyl ammonium bromide/water/1-decanol lyotropic liquid crystalline systems

We report the thermotropic properties and measurements of the temperature and concentration dependences of the refractive index in isotropic micellar L 1 phase and nematic-calamitic N C mesophase of the hexadecyltrimethyl ammonium bromide/water (CTAB/H2O) and hexadecyltrimethyl ammonium bromide/water/1-decanol (CTAB/H2O/DeOH) lyotropic liquid crystalline systems. The effect of amphiphile and aliphatic alcohol concentrations on the refractive properties of L 1 phase and N C mesophase has been studied. Jump-like changes of the refractive properties in regions of the L 1 phase–N C mesophase lyotropic and thermotropic phase transitions have been found. The sufficient effect of CTAB addition on the refractive index value has been found for the CTAB/H2O and CTAB/H2O/DeOH lyotropic systems. In this work, the shape of micelles in L 1 phase and N C mesophase has been also estimated. Estimation showed that structural units of L 1 phase are the isometric spherical micelles, and structural units of N C mesophase are the anisometric rod-like micelles. Typical textures of N C mesophase in the CTAB/H2O and CTAB/H2O/DeOH lyotropic systems and the heterophase regions of the N C mesophase–isotropic liquid thermotropic phase transitions are presented.

Mesomorphism Dependence on Molecular Flexibility by –OCH3 and –H Terminal Units

A novel ester homologous series: 4-(4’-n-Alkoxy benzoyloxy)-4”-methoxy benzyl cinnamates have been synthesized and studied with a view to understanding and establishing the dependence of liquid crystal behavior on molecular structure. The novel series of eleven homologues is entirely nematogenic without exhibition of any smectogenic character from the very first member of the series. Transition and melting temperatures were determined by an optical polarizing microscopy equipped with a heating stage. Transition curves of a phase diagram show the mesomorphism, which behaves in normal manner. An odd-even effect is exhibited by the nematic–isotropic transition curve. The textures of the nematic mesophase are threaded or schlieren in type. Analytical and spectral data confirm the molecular structures of the novel homologues. Thermal stability for the nematic phase is 211.5°C and the degree of mesomorphism varies from 17°C to 72°C and it is a high melting type series. Mesomorphic properties of the series are compared with structurally similar series.

Dependence of Liquid Crystalline Behaviors on Molecular Flexibility

A novel homologous series of thermotropic liquid crystal (LC) has been synthesized with a view to understand and establish the effect of molecular structure on liquid crystal behaviors of a series. The present LC series consist of twelve homologues (C1 to C16); whose mesomorphic properties commence from octyloxy (C8) homologue of a series. C8, C10 and C12 members of a series are monotropic smectic and C14, C16 members are enantiotropically smectogenic. C1 to C7 homologues are nonmesomorphic. Nematogenic property is totally absent. Transition and melting temperatures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of smectic mesophases are focal conic three or two dimensional networking of the type A or C. Cr-I/Sm and Sm-I or I-Sm transition curves behaved in normal manner. Analytical and spectral data confirms the molecular structures of homologues. Thermal stability of smectogenic mesophase is 100.6 oC and mesomorphic phase length is very short (12.9 °C to 15.3 oC). LC properties of a present novel series are compared with the structurally similar homologous series. Present series is partly smectogenic and partly non mesomorphic with poor degree of mesomorphism and middle ordered melting type without exhibition of nematogenic behavior.

Dependence of Molecular Structure on Mesomorphic Behavior with Special Reference to Central Bridge

A novel homologous series of liquid crystalline 4-(4′-n-alkoxy cinnamoyloxy)-4″-methoxy benzyl cinnamates was synthesized and studied with a view to understand and establish the effects of molecular structure on liquid crystal behavior. The series consists of eleven members of the series. None of the homologue derivatives are either nonliquid crystal or smectogenic, i.e. all the eleven members of the novel homologous series are enantiotropcially nematogenic only. Transition and melting temperatures as well as textures of the nematic mesophase were determined on an optical polarizing microscope equipped with a heating stage. The transition curves of the phase diagram show phase behavior in a normal expected manner. An odd-even effect is observed for the nematic-isotropic transition curve. The textures of the nematic mesophase are threaded or Schlieren as determined a by miscibility method. Analytical and spectral data confirm the molecular structures of the homologues. The average thermal stability for nematic is 213.8°C. The isotropic temperatures vary between 190°C and 240°C. The nematogenic mesophase length varies from 17°C to 102°C. Thus, the novel homologous series is entirely nematogenic without the exhibition of smectogenic character. The liquid crystal (LC) properties of the present novel series are compared with structurally similar other known homologous series.

Dependence of Liquid Crystalline Behaviors on Molecular Flexibility

A novel homologous series of thermotropic liquid crystal (LC) has been synthesized with a view to understand and establish the effect of molecular structure on liquid crystal behaviors of a series. The present LC series consist of twelve homologues (C1 to C16); whose mesomorphic properties commence from octyloxy (C8) homologue of a series. C8, C10 and C12 members of a series are monotropic smectic and C14, C16 members are enantiotropically smectogenic. C1 to C7 homologues are nonmesomorphic. Nematogenic property is totally absent. Transition and melting temperatures are determined by an optical polarizing microscopy equipped with a heating stage. Textures of smectic mesophases are focal conic three or two dimensional networking of the type A or C. Cr-I/Sm and Sm-I or I-Sm transition curves behaved in normal manner. Analytical and spectral data confirms the molecular structures of homologues. Thermal stability of smectogenic mesophase is 100.6 oC and mesomorphic phase length is very short (12.9 °C to 15.3 oC). LC properties of a present novel series are compared with the structurally similar homologous series. Present series is partly smectogenic and partly non mesomorphic with poor degree of mesomorphism and middle ordered melting type without exhibition of nematogenic behavior.

Effect of a Central Group on Mesomorphism

A novel homologous series: 4-(4′-n-alkoxy benzoyloxy)-4″-methoxy benzyl benzoates is studied with a view to understanding the effect of a central group on the phenomenon of mesomorphism. The novel homologous series consists of eleven compounds. Mesomorphism commences from the second member of a series. All the mesogenic homologues from ethoxy to hexadecyloxy exhibit nematogenic mesomorphism without the exhibition of smectogenic character. The nematic–isotropic transition curve of the phase diagram behaves in normal manner up to the dodecyloxy homologue and then deviated for the tetradecyloxy and hexadecyloxy homologues. The solid-isotropic or nematic transition curve adopts a normal behavior in a zigzag manner. The nematic-isotropic transition curve shows an odd-even effect and continues up to the octyloxy homologue. Transition and melting temperatures including the textures of mesophases are determined by an optical polarizing microscope, equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type. Analytical data and spectral data support the molecular structures. The mesomorphic behavior of the present series is compared with structurally similar other known series of differing central group (viz. ‒N˭N‒ and ‒CO‒CH˭CH‒) keeping rest of a molecular part unchanged. The nematic thermal stability of the series is 236.8°C of a high melting type present series whose nematogenic mesophase length varies between 27°C and 98°C. Thus, series is only nematogenic without exhibition of a smectic mesophase.