Textures Of Nematic Phase Research Articles

Mesomorphism dependence on molecular rigidity with reference to ‒CH˭CH‒ unit of central bridge

ABSTRACTA novel ester homologous series of rich mesomorphism and low temperatures with unexpected phase behaviors of eleven homologues was synthesized and studied with a view to understanding and establishing the relation between mesomorphic behaviour and the molecular structure of a series 4-(4′-n-alkoxybenzoyloxy)-4″-chlorobenzyl cinnamates. All the members of the novel series are enantiotropically smectogenic and the octyloxy (C8) to hexadecyloxy (C16) homologues are enantiotropically nematogenic, in addition to smectogenic. Odd–even effect is observed for Sm‒I/Sm‒N transition curve but it is absent for N‒I transition curve. Textures of nematic phase are threaded or Schlieren and that of the smectic phase are fan shaped or batonates of smectic-A type phase or Smectic-C type for C16 homologues as judged directly from a heating stage of an optical polarizing microscopy. Analytical and spectral data confirmed the molecular structures of novel homologues. Mesomorphic properties of present series are compared with the structurally similar other known series. The average smectic and nematic thermal stabilities are 92.78°C and 100.8°C, respectively. Mesophase length minimum to maximum for smectic and nematic are 21.0°C to 31.1°C and 8.4°C to 42.6°C respectively. Thus, the present novel series is partly nematogenic and fully smectogenic with considerable degree of mesomorphism and low melting type.

Synthesis of novel ester series and study of its mesomorphism dependence on terminal end group with lateral –OCH3 group

ABSTRACTNovel liquid crystal (LC) materials of ester derivatives were synthesized and studied with a view to understanding and establishing the effects of molecular structure on LC properties. The novel molecules consist of two phenyl rings bonded through –COO– central group and a laterally substituted methoxy group with –OCnH2n+1 as well as –COOCH3 terminal end groups, and yielded 12 homologous members of an ester series. The C1 to C3 members are nonmesomorphic, the C4 to C12 members are enantiotropic nematic only, and the C14 to C16 members are enantiotropically smectogenic in addition to nematogenic. Transition temperatures and the textures of LC state were observed through an optical polarizing microscope (POM) equipped with a heating stage. The textures of nematic phase are threaded or Schlieren, and that of smectic phase are focal conic of the type A or C. Transition curves of a phase diagram behave in normal manner with the exhibition of an odd-even effect (only N-I). Analytical and spectral data support the molecular structures of the novel ester derivatives. The LC properties of the present series are compared with structurally similar other known series. The average thermal stability of the series is 93°C for smectic and 120.88°C for nematic and the mesogenic phase length ranges between 2°C and 46°C.

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.

Mesomorphism and Molecular Structure of Ester Homologous Series Containing Carboxy and Vinyl Carboxy Linking Groups

A novel homologous series 4-(4′-n-alkoxy benzoyloxy)-isopentyl cinnamates consisting of eleven homologs is reported. Mesomorphism commences from the hexyloxy homolog up to the hexadecyloxy homolog. The hexyloxy and hexadecyloxy derivatives are only enantiotropically nematogenic while, but the octyl, decyl, dodecyl, and tetradecyl homologs exhibit enantiotropic nematogenic and smectogenic mesophases. The rest of the homologs are nonmesogenic. The textures of nematic phase are threaded or Schlieren and that of the smectic mesophase is focal conic smectic A or C type. The transition curves of the phase diagram behave in a normal manner without the exhibition of an odd-even effect. Analytical and spectral data confirm the molecular structure of the homologs. Overall mesogenic phase temperature range varies from 11.0°C to 59.0°C. The average thermal stabilities of smectic and nematic are 122.25°C and 139.0°C, respectively. The series is predominantly nematogenic and partly smectogenic with a middle-ordered melting type and a considerable range of liquid crystallinity. Melting points and transition temperatures were determined using an optical polarizing microscope equipped with a heating stage. The mesomorphic properties are compared with structurally similar series.

Study of the Effect of Chalconyl Central Bridge on Mesomorphism

A novel homologous series of chalconyl ester derivatives of thermotropic type of liquid crystals (LC) variety have been synthesized with its general molecular formula RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-N(CH3)2 (Para). Present investigation is planned with a view to understand and establish the relation between molecular structure and the mesomorphic behaviorur of the constituent homologue derivatives as well as to avail novel mesomorphic (LC) substances to the researcher working on multidisciplinary thermotropic LC material with different aims, objects and views at different angles. Novel homologous series consists of twelve homologues C1 to C5 homologues are nonliquid crystals (NLC) and the rest of the C6 to C16 are monotropically nematogenic liquid crystals. Transition temperatures and texture of the LC and NLC were determined by an optical polarizing microscopy equipped with heating stage (POM). Textures of nematic phase are threaded or schlieren. Analytical and spectral data confirms the molecular structures of homologues. Thermal stability for monotropy is very low of the magnitudes of few second and of negligible degree of temperature difference. Thermal properties of present novel series are compared with of structurally similar series, data interpreted in terms of molecular rigidity and flexibility to derive group efficiency order.

Study of the Effect of Chalconyl Central Bridge on Mesomorphism

A novel homologous series of chalconyl ester derivatives of thermotropic type of liquid crystals (LC) variety have been synthesized with its general molecular formula RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-N(CH3)2 (Para). Present investigation is planned with a view to understand and establish the relation between molecular structure and the mesomorphic behaviorur of the constituent homologue derivatives as well as to avail novel mesomorphic (LC) substances to the researcher working on multidisciplinary thermotropic LC material with different aims, objects and views at different angles. Novel homologous series consists of twelve homologues C1 to C5 homologues are nonliquid crystals (NLC) and the rest of the C6 to C16 are monotropically nematogenic liquid crystals. Transition temperatures and texture of the LC and NLC were determined by an optical polarizing microscopy equipped with heating stage (POM). Textures of nematic phase are threaded or schlieren. Analytical and spectral data confirms the molecular structures of homologues. Thermal stability for monotropy is very low of the magnitudes of few second and of negligible degree of temperature difference. Thermal properties of present novel series are compared with of structurally similar series, data interpreted in terms of molecular rigidity and flexibility to derive group efficiency order.

Molecular Rigidity/Flexibility Dependence of Mesomorphism

A novel chalconyl homologous series of liquid crystalline derivatives; RO - C6H4- CH : CH - COO - C6H4-CO - CH : CH - C6H4 - OC8H17 (n) (para) have been synthesized and studied with a view to correlate the thermotropic liquid crystal (LC) behavioural properties and the molecular structure of a substance. Present novel series consisted of eleven homologue members (C1 to C16) whose, only nematogenic mesomorphism commences from C3 homologue and continued upto C16 homologue in enantiotropic manner with absence of smectogenic character. Transition temperatures and textures of nematic phase were determined using an optical polarizing microscopy equipped with a heating stage (POM). Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibited odd-even effect and deviated from its normal descending tendency from and beyond C8 homologue and adopted serpantile shape from C8 to C16 homologue in deviating manner. Textures of the nematic phase are threaded or schlieren. Analytical and spectral data supported molecular structures of homologues. Thermal stability for nematic is 112.66 and the degree of mesomorphism vary from 5.00C to 44.00C at the C12 andC4 homologue respectively. It is a middle ordered melting type series, whose relative group efficiency order for nematic derived.

Effect of Equipolar Endgroup of a Molecule on Mesomorphic-Isotropic Transition Curve

A Homologous series:RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-OC18H37(n) (para) of chalconyl novel ester of dual character as thermotropic and lyotropically bioactive is synthesized and studied with a view to understand and establish the relation between mesomorphism and molecular structure on the basis of molecular rigidity and flexibitity through thermotropic liquid crystalline (LC) state. Novel series consists of thirteen homologues of which four homologues (C1 to C4) are non liquid crystal (NLC) and the rest of the homologues (C5 to C18) are thermotropically enantiotropic nematic without exihibition of smectic property. Thermometric transition temperatures and textures of nematogenic phase are determined by an optical polarizing microscopy equipped with a heating stage (POM).Textures of nematic phase are threaded or schilieren. Transition temperatures of novel homologues are relatively lower than the transition temperature of corresponding dimeric trans n-alkoxy cinnamic acid. Cr-N/I and N-I transition curves behaves in normal manner with negligible abnormality at C18 homologue in phase diagram of a series.Analytical and spectral data conforms the molecular structure of homologues. Thermal stability for nematic is 121.88°C whose degree of mesomorphism vary minimum from 4.0°C to a maximum of 34.0 °C, and hence novel series is of middle ordered melting type, Group efficiency order for-OC18H37 tail groups (series-1&Y) is highest irrespective of type of ester group –COO-and CH=CH-CO derived for nematic.

Study of Molecular Flexibility Operated Mesomorphism

Homologous series RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-OC14H29(P) of chalconyl novel derivatives have been synthesized and studied with a views to understand and establish the relation between molecular structure and the liquid crystal (LC) properties of thermotropic mesomorphs Series consists of thirteen homologues. Five homologues (C1 to C5) are nonliquid crystal (NLC) and the rest of the homologues (C6 to C18) are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and textures were determined by an optical polarizing microscope equipped with a heating stage (POM). Transition curves of a phase diagram (N-I and Cr-I/N) behaved in normal manner. N-I transition curve exhibited odd-even effect with negligible abnormality in its behaviour at the C14 homologue. Thermal stability for nematic is 99.75°C.The degree of mesomorphism vary minimum 19°C at the C6 homologue to maximum 28°C at the C8 homologue. Analytical and spectral data confirms the molecular structures of the novel homologues. Evaluated thermal data of present novel series are compared with other structurally similar homologous series. Textures of Nematic phase are threded or schlieren.

Molecular Rigidity/Flexibility Dependence of Mesomorphism

A novel chalconyl homologous series of liquid crystalline derivatives; RO - C6H4- CH : CH - COO - C6H4-CO - CH : CH - C6H4 - OC8H17 (n) (para) have been synthesized and studied with a view to correlate the thermotropic liquid crystal (LC) behavioural properties and the molecular structure of a substance. Present novel series consisted of eleven homologue members (C1 to C16) whose, only nematogenic mesomorphism commences from C3 homologue and continued upto C16 homologue in enantiotropic manner with absence of smectogenic character. Transition temperatures and textures of nematic phase were determined using an optical polarizing microscopy equipped with a heating stage (POM). Transition curve Cr-N/I behaved in normal manner. N-I transition curve exhibited odd-even effect and deviated from its normal descending tendency from and beyond C8 homologue and adopted serpantile shape from C8 to C16 homologue in deviating manner. Textures of the nematic phase are threaded or schlieren. Analytical and spectral data supported molecular structures of homologues. Thermal stability for nematic is 112.66 and the degree of mesomorphism vary from 5.00C to 44.00C at the C12 andC4 homologue respectively. It is a middle ordered melting type series, whose relative group efficiency order for nematic derived.

Effect of Equipolar Endgroup of a Molecule on Mesomorphic-Isotropic Transition Curve

A Homologous series:RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-OC18H37(n) (para) of chalconyl novel ester of dual character as thermotropic and lyotropically bioactive is synthesized and studied with a view to understand and establish the relation between mesomorphism and molecular structure on the basis of molecular rigidity and flexibitity through thermotropic liquid crystalline (LC) state. Novel series consists of thirteen homologues of which four homologues (C1 to C4) are non liquid crystal (NLC) and the rest of the homologues (C5 to C18) are thermotropically enantiotropic nematic without exihibition of smectic property. Thermometric transition temperatures and textures of nematogenic phase are determined by an optical polarizing microscopy equipped with a heating stage (POM).Textures of nematic phase are threaded or schilieren. Transition temperatures of novel homologues are relatively lower than the transition temperature of corresponding dimeric trans n-alkoxy cinnamic acid. Cr-N/I and N-I transition curves behaves in normal manner with negligible abnormality at C18 homologue in phase diagram of a series.Analytical and spectral data conforms the molecular structure of homologues. Thermal stability for nematic is 121.88°C whose degree of mesomorphism vary minimum from 4.0°C to a maximum of 34.0 °C, and hence novel series is of middle ordered melting type, Group efficiency order for-OC18H37 tail groups (series-1&Y) is highest irrespective of type of ester group –COO-and CH=CH-CO derived for nematic.

Study of Molecular Flexibility Operated Mesomorphism

Homologous series RO-C6H4-CH=CH-COO-C6H4-CO-CH=CH-C6H4-OC14H29(P) of chalconyl novel derivatives have been synthesized and studied with a views to understand and establish the relation between molecular structure and the liquid crystal (LC) properties of thermotropic mesomorphs Series consists of thirteen homologues. Five homologues (C1 to C5) are nonliquid crystal (NLC) and the rest of the homologues (C6 to C18) are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and textures were determined by an optical polarizing microscope equipped with a heating stage (POM). Transition curves of a phase diagram (N-I and Cr-I/N) behaved in normal manner. N-I transition curve exhibited odd-even effect with negligible abnormality in its behaviour at the C14 homologue. Thermal stability for nematic is 99.75°C.The degree of mesomorphism vary minimum 19°C at the C6 homologue to maximum 28°C at the C8 homologue. Analytical and spectral data confirms the molecular structures of the novel homologues. Evaluated thermal data of present novel series are compared with other structurally similar homologous series. Textures of Nematic phase are threded or schlieren.

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 and Molecular Structure: Novel Homologous Series 4-(4′-n-alkoxy cinnamoyloxy)-4′′-methoxy Benzyl Benzoates

A novel homologous series consists of 11 homologues, studied with a view to understand and establish the relations between mesomorphism and molecular structure of novel substances. All the novel members of a series except methoxy and pentyloxy homologue derivatives are liquid crystalline [LC] in nature. Mesomorphism commences from a second member of a series ethoxy, propyloxy, butyloxy, and hexyloxy to hexadecyloxy homologue derivatives are nematogenic while decyloxy, dodecyloxy, and tetradecyloxy homologue derivatives are smectogenic, in addition to nematogenic. All mesogenic homologues of a series are enantiotropic mesomorphic. Phase transition curve for Smectic-Nematic behave in normal manner without exhibition of odd-even effect, whereas nematic-isotropic transition curve adopts serpentile shape as rising and falling nature with exhibition of very minor odd-even effect. Textures of nematic phase are threaded or schlieren and that of a smectic mesophase is a focal conic fan shaped of the type smectic A or C. Analytical and spectral data supported molecular structures of homologues. The mesomorphic behaviors of present series are compared with a structurally similar other known series. Smectic and nematic thermal stabilities are 182.6 and 246.0°C, respectively. Present series is partly smectogenic and predominantly nematogenic with considerable degree of mesomorphism (maximum 100 °C) and high melting type.

SYNTHESIS OF LIQUID CRYSTALLINE COPOLYESTERS WITH T-SHAPED TWO-DIMENSIONAL MESOGENIC UNIT AND CROWN ETHER CYCLE

A novel series of liquid crystalline copolyesters with T-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4′-(α,ω-hexanedioyloxy)dibenzoyl dichloride (M1), 2-(4′-ethoxyphenyl)hydroquinone (M2) and cis-4,4′-bis(4-hydroxyphenylazo)dibenzo-18-crown-6 (M3). The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.29–0.43. The monomers' structures were identified by elemental analysis, IR, UV, 1 H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHCl3 at room temperature except CP-9. The properties of copolyesters were investigated by using GPC, [η], DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystalline phase when they were heated to above their melting temperature (Tm). The threaded texture and schlieren texture of nematic phase can be observed on POM. Their...