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Patel H.B.,Baroda Textile Effects Pvt. Ltd | Doshi A.V.,Dr K.N. Modi University
Molecular Crystals and Liquid Crystals | Year: 2015

A novel homologous series 4-(4'-n-alkoxy benzoyloxy) benzyl cinnamates was synthesized and studied with a view to understanding and establishing the relationships between mesomorphism and molecular structure. The novel series consists of eleven members with the commencement of mesomorphism from the pentyloxy homologue onwards to the hexadecyl homologue. The remaining homologues are nonmesomorphic. All the mesomorphic homologues exhibit smectogenic mesomorphism in addition to nematogenic mesomorphism for a definite temperature range in an enantiotropic manner, except for the pentyloxy homologue, which exhibits only a nematogenic mesophase in an enantiotropic manner without the formation of a smectic phase. The texture of the nematic mesophase is of the threaded or Schlieren type and the smectic mesophase is of the type A or C texture, as determined by a miscibility method. Transition temperatures were observed through an optical polarizing microscope equipped with a heating stage. The transition curves of a phase diagram predominantly behave in a normal manner, but partly deviated from normal behavior with the exhibition of an odd-even effect. Analytical and spectral data confirms the molecular structures of all homologues. The mesomorphic behavior of the present series is compared with other structurally similar known series. The mesomorphic temperatures vary between 106°C and 180°C. The mesophase length varies between 33°C to 53°C. Thus, the novel series is predominantly nematogenic and partly smectogenic with relatively high transition temperatures and is of a high melting type. The average thermal stabilities for smectic and nematic phases are 144.1°C and 171.4°C, respectively. © 2015 Copyright © Taylor & Francis Group, LLC. Source


Patel B.H.,Baroda Textile Effects Pvt. Ltd | Doshi A.V.,Dr K.N. Modi University
Molecular Crystals and Liquid Crystals | Year: 2015

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. Copyright © 2015 Taylor & Francis Group, LLC. Source


Patel B.H.,Baroda Textile Effects Pvt. Ltd | Doshi A.A.,M. S. University of Baroda | Doshi A.V.,Dr K.N. Modi University
Molecular Crystals and Liquid Crystals | Year: 2015

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. © 2015 Taylor & Francis Group, LLC. Source


Patel B.H.,Baroda Textile Effects Pvt. Ltd | Vyas N.N.,P.A. College | Doshi A.V.,Dr K.N. Modi University
Molecular Crystals and Liquid Crystals | Year: 2015

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. NN and COCHCH) 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. © 2015 Taylor & Francis Group, LLC. Source


Patel B.H.,Baroda Textile Effects Pvt. Ltd | Doshi A.V.,Dr K.N. Modi University
Molecular Crystals and Liquid Crystals | Year: 2014

A novel ester homologous series of 4-[4-n-alkoxy cinnamoyloxy] benzyl benzoates has been synthesized. The series consists of 12 homologues. Liquid crystal properties commence from the sixth member to the last member of the series with the exhibition of an enantiotropic nematic phase without the exhibition of any smectogenic mesophase. The remaining homologues do not exhibit liquid crystal behavior. The texture of the nematic phase is of the threaded or Schlieren type. The solid-nematic or isotropic transition curve adopts a zigzag path and the nematic-isotropic transition curve steeply rises and then falls in the phase diagram and behaves in normal manner. An odd-even effect is absent in the nematic-isotropic transition curve with an alteration of transition temperatures. The average thermal stability for the nematic mesophase is 153.1°C, and the nematogenic temperature ranges vary from 12°C to 50°C. Analytical data confirm the molecular structures of the homologues. The Liquid Crystal properties and transition temperatures were observed through an optical polarizing microscope, equipped with a heating stage. The mesomorphic characteristics of the novel ester series are compared with other, known and structurally similar series. The novel series is predominantly nematogenic with the absence of any smectogenic character, with relatively short mesophase temperature ranges and of the middle ordered melting type. © 2014 Copyright © Taylor & Francis Group, LLC. Source

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