Vinay S. Sharma

Molecular structure and mesomorphism: Effect of tail/lateral group

ABSTRACT Chalconyl homologous series of novel mesogenic substances of molecular structure RO-C6H4-COO-C6H4-CO-CH:CH-C6H4-OC16H33 (P) has been studied with a view to understanding and establishing the effects of molecular structure on liquid crystal (LC) properties. A novel homologous series consists of 13 (C1 to C18) members. C1 to C5 and C7 members are non-mesogenic and the even numbered C6 to C18 homologues are enantiotropically nematogenic with absence of smectogenic property. Thermotropic properties such as phase transition temperatures and textures (threaded or Schlieren) were determined by an optical polarizing microscopy equipped with a heating stage. Analytical and spectral data confirm the molecular structure. Transition curves (Cr-N and N-I) showing phase behaviors in phase diagrams behave in a normal manner except C16 and C18 homologues, which partially deviate from normal behavior in N-I transition curve. Thermal stability for nematic on average is 113.14°C and the total mesophase length ranges from 10 to 26°C. The usual odd-even effect is absent for the N-I transition curve. The LC properties of the present novel series are compared with structurally similar known series. The present novel series is predominantly nematogenic without exhibition of smectogenic character, and is of a lower middle-ordered melting-type.

Dependence of thermotropic mesomorphism on molecular flexibility of changing tail group

ABSTRACT A novel chalconyl ester homologous series of liquid crystals has been synthesized and studied with a view to understanding and establishing the effect of molecular structure on liquid crystalline properties. Novel series consisted of 13 members (C1–C18) of a series. C1–C4 member of a series is nonliquid crystals and, the rest of the homolog members (C5–C18) are enantiotropically nematogenic with absence of smectogenic property. None of the homolog is monotropically mesomorphic. Transition and melting temperatures were determined by an optical microscope equipped with a heating stage. Textures of nematic phase are threaded or schlieren. Spectral and analytical data of selected members of a series confirms the molecular structures of homologues. Cr-N and N-I transition curves of a phase diagram behaved in normal manner with exhibition of odd-even effect of very short range as observed for N-I transition curve. Thermal stability for nematic is 122.0°C and the nematogenic mesophase ranges from 7.0°C to 38.0°C. Liquid crystal properties of a present series are compared with the structurally similar known homologous series.

Molecular flexibility dependence mesomorphism

ABSTRACT A 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.

Study of mesomorphism and its relation to molecular structure with special reference to central bridges viz. -COO- and -CH=CH-COO- of the homologous series

GRAPHICAL ABSTRACT Abstract Two ester homologous series of mesogens, viz., Methyl-p-(p′-n-alkoxy benzoyloxy) cinnamates (X) and Methyl-p-(p′-n-alkoxy cinnamoyloxy) cinnamates (Y) being structurally similar are discussed. Both (X) and (Y) differ in respect of central bridges linking two phenyl rings. Only enantiotropic nematogenic character is observed without exhibition of any smectic character by all members of series (X) and (Y). Thermal stability of series (X) is relatively low as compared to (Y), but nematogenic mesophase lengths are of reverse order. Solid-nematic/solid-isotropic and nematic-isotropic transition curves in the phase diagrams behave in normal manner.

Mesomorphism dependence on molecular rigidity and substitution of same functional group on lateral or terminal position of tailed phenyl ring

ABSTRACT Novel liquid crystal materials (LCs) of low temperature range (53°C to 75°C) have been synthesized through a series of chalconyl derivatives consisting of two phenyl rings bonded through a –CH˭CH‒CO‒ central bridge to study the effect of molecular structure on LC properties in general and with a focus on molecular rigidity. The novel homologues series (C1 to C18) consists of thirteen homologues with general formula RO‒C6H4‒CH˭CH‒CO‒C6H4‒OC10H21(n) (meta). The C1, C2, C3 homologues are nonliquid crystals (NLC) and the rest of the homologues (C4 to C18) are either monotropic or enantiotropic liquid crystals. C4 to C6 homologues are enantiotropicnematic and the rest of the mesomorphic homologues are (C7 to C18) monotropicsmectic in addition to monotropicnematic character. Transition and melting temperatures including textures of homologues were determined by an optical polarizing (POM) microscopy equipped with a heating stage. Textures of a nematic phase are threaded or Schlieren, and that of the smectic phase are of the type Smectic A or C as judged directly from the heating top of the microscope. Thermal stability for smectic is very poor and of the nematic is (N-I) 69.3°C whose, total mesophase length ranges between 07.0 to 14.0°C at C8 and C4 homologues respectively.

Design and investigation of calamatic liquid crystals: Schiff base (‒CH˭N), chalcone (‒CO‒CH˭CH‒), and ester (‒COO‒) linkage group contain rigid rod shape with various terminal parts

GRAPHICAL ABSTRACT ABSTRACT The mesomorphic properties of linear schiff base-chalconyl ester homologous series can be designed in a predictable fashion with using various alcohol and para-tert-butyl phenol. We have synthesized total 14 novel liquid crystalline compounds and divided into two parts, i.e, series-1 (D1 to D10) and series-2 (E1 to E4). The result of both the series are compared and discussed. These compounds possess a rod-like geometry with rigid linear spacers and possessing smectic C and smectic A phases, while nematogenic phase was achieved by increasing the flexibility and broadening of tail-ended group in molecule. The texture image of mesophases is needle; rod like; broken fan type and nematic texture images are the type of schlieren and threaded in some homologue. All these compounds were characterized by elemental analyses and spectroscopic techniques such as FTIR and 1H and 13C [NMR] spectroscopies. The mesomorphic properties of these compounds were observed by optical polarized light microscopy and differential scanning calorimetry.

Effect of alkyl chain in the terminal ester group on mesomorphic properties of new rod like homologous series: Synthesis and characterization

GRAPHICAL ABSTRACT ABSTRACT The mesomorphic properties of linear chalconyl ester homologous series can be tuned in a predictable fashion with tail groups (‒OC5H11) substituents on the terminal side and nitro group substitute at lateral position. Novel series consisted 13 members (C1 to C8, C10, C12, C14, C16, C18). C1 to C5 homologues are nonliquid crystal, C6 to C18 homologues display smectic and nematic mesophase enantiotropically manner except C5 homologue, which show only nematogenic mesophase. The texture of the nematic mesophase is of fan-shaped, Schlieren, and nematic droplets type. All these compounds were characterized by elemental analyses and spectroscopic techniques such as [FTIR] and 1H Nuclear magnetic resonance [NMR] spectroscopy. The mesomorphic properties of these compounds were observed by optical polarized light microscopy (POM) and differential scanning calorimetry (DSC).

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

Synthesis and study of mesomorphic properties of azoester compounds

ABSTRACT In order to investigate the influence of the terminal substitution on mesomorphism, the newly synthesized homologues series based on azoester have been synthesized. The influence of the structure of the mesogenic core has been present in this study, effect of hydrocarbon chain length and flexibility at terminal side effect on mesomorphism was represents in this case. In this investigation, we represent a series consisting of thirteen (C1–C18) homologue. In which, C1 to C3 homologue are nonmesomorphic. While C4–C18 shows smectic as well as nematic mesophase enantiotropically. Analytical and spectral data confirmed the molecular structures of homologues. All these compounds were characterized by elemental analysis and Fourier transform infrared [FTIR] and 1H NMR. Their mesomorphic properties were measured by optical polarized light microscopy and differential scanning calorimetry (DSC) and PXRD.

The effect of position of tert-butyl tail group on the formation of liquid crystal in Schiff base ester based homologous series

GRAPHICAL ABSTRACT ABSTRACT We report a newly rod like calamatic liquid crystalline materials, which are constructed by the self-organization of a rod-like carboxylic acid derivative based on Schiff base ester as the linking group with tert butyl tail group. A newly series of 4-(tert-butyl) phenyl 4-((4-alkoxybenzylidene) amino) benzoate with different alkyl chain spacer (n = 1 to 8, 10, 12, 14, 16, and 18) were synthesized and their mesomorphic properties were investigated by differential scanning calorimetry and polarized optical microscopy. All homologous in present series displays mesophase in enantiotropically manner. Thermal stability of SmC-SmA is 137.5 °C. All the compounds were characterized by spectroscopic and elemental analysis. The effects of varying left alkyl side spacer on mesomorphism with its structurally related compounds in series have been discussed.