B. B. Jain

Study of the mesomorphism of benzoates and cinnamates

ABSTRACT 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. GRAPHICAL ABSTRACT

Molecular flexibility operated mesomorphism by end groups in azoester series

ABSTRACT A novel azoester homologous series, RO‒C6H4‒COO‒C6H4‒N = N‒C6H4‒OC7H15(n) (para) has been synthesized and studied with a view to understanding and establishing the effects of molecular structure on mesomorphic properties with reference to tthe flexible terminal chain. The novel azoester series consists of thirteen (C1–C18) members. Mesomorphism commences from C5 homologue. C1–C4 homologues are nonmesomorphic, C5 homologue is only nematogenic and C6–C18 homologues are smectogenic and nematogenic. All mesogenic homologues are enantiotropically mesomorphic. Transition temperatures and textures were determined by polarizing optical microscopy (POM) and a heating stage. Cr-M/I transition curve follows a zigzag path of rising and falling values and behaves in a normal manner. The Sm-N and N-I transition curves of a phase diagram behave in the normal established manner except for a small deviation for the higher homologues (C14 and C16). An odd-even effect is exhibited by Sm-N and N-I transition curves. Analytical spectral and thermal data support the molecular structures. Smectic and nematic thermal stabilities are 93.62°C and 114.3°C, respectively. Smectic and nematic mesophas elengths range from 12.0°C to 18.0°C and 11.0°C to 31.0°C. The series is predominantly nematogenic and partly smectogenic and of middle order melting type. Group efficiency order derived for smectic and nematic. Smectic and nematic: ‒OCH3 > ‒OC4H9 > ‒OC7H15(n).

Synthesis, characterization and study of liquid crystal properties of new homologous chalcone series

GRAPHICAL ABSTRACT ABSTRACT One new mesogenic homologous series of chalconyl derivative with two ring (3/-(4/- (decyloxy) phenyl-1-(4-(alkoxy) phenyl) prop-2-en-1-one) has been synthesized and characterized by a combination of elemental analysis and standard spectroscopic methods. In the series, the lower members (C4 and C5) exhibit only enantiotropic nematic mesophase but middle and higher members exhibit enantiotropic nematic as well as smectic mesophase. The nematic mesophase commence from C4 homologue and smectic mesophase (smectic-A type texture) commence from C6 homologue as enantiotropic and persists up to the last member synthesized. The mesomorphic properties of present series were compared with other two structurally similar series to study the effects of change of meta and para position on the mesomorphism.

Mesomorphism of azo-esters and chalcone-esters

ABSTRACT One chalcone-ester homologous series of mesogens α-4-[4/-n-alkoxybenzoyloxy phenyl β-4//methoxy benzoyl ethylenes (A) and one azo-ester homologous series of mesogens p-(p/-n-alkoxybenzoyloxy) phenyl azo-p//-methoxy benzene (B) being structurally similar are discussed. Both series (A) and (B) differ in respect of central bridges linking two phenyl rings. Mesomorphic properties start from 6th and 1st member of series (A) and (B) respectively. In series (A), 6th to 12th members show both smectogenic and nematogenic properties, and the 14th and 16th members show only nematogenic property. While in series (B), 1st to 10th members show nematogenic properties, 11th member shows both smectogenic and nematogenic properties, while 12th member shows only smectogenic property. Thermal stability of series (A) is relatively high as compared to series (B). Transition temperatures are observed through hot stage polarizing microscope by the miscibility method. Analytical data support the structure of molecules. Textures of series (A) in nematic are threaded and Schlieren in SmecticSmectic A type, while that of series (B) in nematic are threaded in SmecticSmectic A and smectic C. GRAPHICAL ABSTRACT

Synthesis and study of new homologous series of ester-chalcone exhibiting nematic phases

GRAPHICAL ABSTRACT ABSTRACT A novel homologous series of ester-chalcone have been synthesized and their liquid crystals (LCs) properties are studied. All the homologue shows nematic phase except C1−C4 homologue. Classical nematic textures are observed in this homologous series with the help of polarizing optical microscope (POM) equipped with hot stage. The role of flexible methylene group spaces, degree of polymerization and central linkage on the exhibition of all the homologue is discussed. The novel homologous series has been characterized by the standard methods (1HNMR, IR, and elemental analysis).

Dependence of mesomorphism on molecular rigidity of nonlinear and linear isomeric and nonisomeric chalconyl esters

ABSTRACT The novel thermotropic liquid crystalline (LC) materials have been synthesized and studied through chalconyl ester nonlinear (meta substituted) homologous series RO-C6H4‒CH˭CH‒COO‒C6H4-CO‒CH˭CH‒C6H4-OC14H29(n) with a view to understand the effect of molecular structure on LC behavior with reference to determine the difference between linear and nonlinear shaped molecules. Novel series consisted of thirteen members, whose nematogenic enantiotropic mesomorphism commences from C6 homologue and continued up to C18 homologue with the absence of smectogenic character. C1 to C5 homologues are nonliquid crystals as determined through an optical polarising microscope (POM) equipped with a heating stage. Transition temperatures of LC homologues alternate and are lower than the corresponding n-alkoxy cinnamic acids. Cr-N/I and N-I transition curve behaved in normal manner. N-I transition curve exhibited odd-even effect in a phase diagram. Textures of nematic phase are threaded or Schlieren or determined by miscibility method and from observing mesophase on the top of the POM. Thermal stability for nematic is 92.5 and mesophase length minimum to maximum is 19.0 to 32.0°C at the C10/18and C6 homologue. Group efficiency order on the basis of thermal stability is Thus, novel series is nematogenic and low melting type. Analytical and spectral data confirmed the molecular structures of homologues.

Dependence of LC state on molecular flexibility

ABSTRACT A novel azoester homologous series of liquid crystals (LCs) viz. RO‒C6H4COOC10H6-N˭N(ortho)-C6H4‒OC4H9(para) has been synthesized and studied with a view to understanding and establishing the effect of molecular structure on LC properties. Homologous Series consists of thirteen members (C1 to C18). C1 to C3 members are nonliquid Crystals and the rest of the homologues are LC in an enantiotropic manner. C7 to C18 are smectogenic in addition to nematogenic whereas C4, C5, and C6 are only nematogenic. The Sm-N and N‒I transition curves behave in a normal manner with the usual exhibition of an odd–even effect. The Cr-M/I curve also behaves in a normal manner. Analytical and spectral data confirm the molecular structures of homologues. The average smectic and nematic thermal stabilities are 60.31°C and 79.6°C, respectively, with total mesophase length varying minimum to maximum is 21°C to 57°C at the C6 and C14 homologue, respectively. Thus, present novel azoester homologous series is partly smectogenic and predominantly nematogenic with low ordered melting type and useful to construct LC devices workable at low temperatures or room temperature.

Synthesis and mesomorphism of novel chalconyl esters with a lateral nitro group

ABSTRACT A new chalconyl homologous novel series with lateral nitro group: 4-(3-4-(heptyloxy)phenyl) acryloyl-2/-nitro phenyl 4′-alk oxy benzoate have been synthesized and all the members are differed by the terminal chain length CnH2n+1, where n = 1,2,3,4,5,6,7,8,10,12,14,16,18. Their transition temperatures and mesophase characteristics are studied with the help of polarizing optical microscope (POM). All 13 homolog of series except the C1–C4 are enantiotropically mesogenic. The molecular structures have been confirmed by the analytical techniques of NMR, IR, and elemental analysis. GRAPHICAL ABSTRACT

Synthesis and mesomorphic behavior of liquid crystal chalconyl esters

ABSTRACT A chalconyl homologous novel series of thermotropic liquid crystals (LC) have been synthesized and studied with a view to understand and establish the effects of molecular structure on LC properties in thermotropic behaviors. Homologous series consists of 13 homologs (C1–C18), C1–C4 homologs are nonliquid crystals and the rest of the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and the textures of the nematic phase were determined by an optical polarizing microscopy, equipped with a heating stage (POM). Texture of a nematic phase are threaded or Schlieren. The Spectral and analytical data confirms the molecular structures of homologs. Cr-N/I and N-I transition curves behaved in normal manner except C7 homolog which shows negligible abnormality for N-I transition temperature or curve with exhibition of odd-even effect.

Mesomorphism dependence on tail group

ABSTRACT A chalconyl homologous novel series of thermotropic liquid crystals (LC) have been synthesized and studied with a view to understand and establish the effects of molecular structure on LC properties in thermotropic behaviors. Homologous series RO-C6H4-COO-C6H4-CO-CH=CH-C6H4-OC14H29 consists of 13 homologs (C1–C18), C1–C6 homologs are nonliquid crystals and the rest of the homologs are enantiotropically nematogenic without exhibition of smectic property. Transition temperatures and the textures of the nematic phase were determined by an optical polarizing microscopy, equipped with a heating stage. Texture of a nematic phase are threaded or schlieren. The Spectral and analytical data confirms the molecular structures of homologs. Thermal stability for nematic is 123.0°C and its mesogenicphaselength ranges between 13°C and 34°C. Cr-N/I and N-I transition curves behaved in normal manner except C14 homolog which shows negligible abnormality for N-I transition temperature or curve with exhibition of odd-even effect. Some LC properties are compared with the structurally similar homologous series. Thus, present homologous series is nematogenic and middle ordered melting type.