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Chauhan H.N.,University of Rajasthan | Chauhan H.N.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,University of Rajasthan
Molecular Crystals and Liquid Crystals | Year: 2013

A novel homologous series consists of 12 compounds. The shorter chain homologues do not show liquid crystal phases, but from six carbons onwards, the nematic phase is exhibited enantiotropically, with some members also showing a smectic phase. The phase behavior of the transition curves of the series shows a usual trend. The texture of the nematic phase is the threaded or Schlieren type and that of smectic phase is a smectic A. An odd-even effect is observed for smectic-nematic and nematic-isotropic transition curves. Analytical data confirm the molecular structure. The transition temperatures were determined by an optical polarizing microscopy. The mesogenic properties of the novel series are compared with a structurally similar homologous series. The average smectic-nematic and nematic-isotropic thermal stabilities are 133.4°C and 159.8°C, respectively, with a mesogenic temperature range of 10°C to 62°C. © 2013 Copyright Taylor and Francis Group, LLC.


Chaudhari R.P.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,University of Rajasthan
Molecular Crystals and Liquid Crystals | Year: 2013

The synthesis and mesomorphic properties of a novel homologous series is reported. With the exception of the methyl and ethyl homologues, all 11 members of the series exhibit mesomorphism enantiotropically. The propyl to pentyl homologues, and the tetradecyl and hexadecyl homologues are enantiotropic nematic without the exhibition of smectic mesomorphism; while the hexyl to dodecyl homologues exhibit smectic mesomorphism in addition to the nematic phase. The texture of the nematic-mesophase by optical polarizing microscopy is of the threaded or Schlieren type, and that of smectogenic homologues is of the focalconic fan type. A phase diagram of the series shows a typical trend. Analytical and spectral data confirm the molecular structure of the compounds. Transition temperatures and mesomorphic properties are determined by optical polarizing microscopy. Smectic and nematic thermal stabilities are 125°C and 167°C, respectively. The series is predominantly nematogenic and partly smectogenic with middle-order melting type, and the smectic and nematic-mesophase ranges vary from 8°C to 22°C and 9°C to 56°C, respectively. The mesomorphic properties of the novel series are compared with other structurally similar homologous series. © 2013 Copyright Taylor and Francis Group, LLC.


Chauhan H.N.,K K Shah Jarodwala Maninagar Science College | Shah R.R.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,Jagdishprasad Jhabarmal Tibrewala University
Molecular Crystals and Liquid Crystals | Year: 2013

A novel homologous series of liquid crystals, viz., α-4-[4′-n- alkoxy cinnamoyloxy] benzoyl-β-4″-chloro phenyl ethylenes, has been synthesized. The series consists of twelve homologs. The methyl to butyl derivatives are not liquid crystalline and the rest of the homologs are enantiotropic liquid crystals. The octyl to dodecyl derivatives of the series are enantiotropically smectogenic in addition to nematogenic in character, but the pentyl, hexyl, heptyl tetradecyl, and hexadecyl homolog derivatives of the series are only nematogenic without the exhibition of a smectic phase. The transition temperatures of the novel substances were determined by optical polarizing microscopy equipped with a heating stage. A plot of transition temperatures versus the number of carbon atoms present in the n-alkoxy terminal chain represents the phase behavior of the series. An odd-even effect is observed for the nematic-isotropic transition curve. The textures of the nematic phase are of a threaded or Schlieren type and those of the smectic A and smectic C phases are typical. Analytical and spectral data agree with the molecular structures. The smectic and nematic thermal stabilities are 132.6°C and 156.7°C, respectively. The smectic phase commences from the octyloxy homolog. Smectogenic phase lengths vary from 26°C to 33°C and the nematogenic phase lengths vary from 6°C to 70°C. The series is predominantly nematogenic and partly smectogenic with considerable mesophase length and a middle-ordered melting type. The liquid crystal properties of the present series are compared with structurally similar homologous series. © 2013 Taylor & Francis Group, LLC.


Chauhan H.N.,K K Shah Jarodwala Maninagar Science College | Vyas N.N.,P.A. College | Doshi A.V.,Jagdishprasad Jhabarmal Tibrewala University
Molecular Crystals and Liquid Crystals | Year: 2013

A novel homologous series entitled α-4-[4′-n-Alkoxy benzoyloxy] benzoyl β-4″-chloro phenyl ethylenes consists of 12 homologues. The pentyl to tetradecyl homologues are enatiotropically nematogenic and all of the other homologues (methyl to butyl and hexadecyl) are nonmesogenic. The textures of the nematogenic mesophase are threaded or Schlieren in nature. The transition temperatures were determined by an optical polarizing microscope with a heating stage. The phase diagram of the novel series shows a normal behavior with negligible abnormality in trend of the nematic-isotropic transition curve and exhibits an odd-even effect as expected. The nematic thermal stability is 149.4°C on average. The series is nematogenic without any smectogenic character. The mesogenic properties of the novel series are compared with known series that are structurally similar. © 2013 Copyright Taylor and Francis Group, LLC.


Suthar D.M.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,University of Rajasthan
Molecular Crystals and Liquid Crystals | Year: 2013

The synthesis and mesomorphic properties of a novel homologous series entitled α-4-[-4′-n-Alkoxy benzoyloxy] phenyl β-4 ″-nitro benzoyl ethylenes are reported. All the 11 members of the series except the methoxy and ethoxy derivatives are mesogenic. The propyloxy to pentyloxy and the hexadecyloxy homologues are only enantiotropically nematogenic and the rest of the mesogenic homologues are enantiotropically smectogenic in addition to nematogenic in character. A phase diagram shows the phase behavior through transition curves is of a normal type. An odd-even effect is observed for the nematic-isotropic transition curve. Analytical and spectral data support the molecular structure of the materials. Transition temperatures and other liquid crystal (LC) properties including average thermal stabilities for smectic and nematic were determined by optical polarizing microscopy. Average thermal stability for smectic and nematic are 125.6°C and 154.6°C, respectively. Smectogenic and nematogenic phase ranges vary between 19°C to 35°C and 14°C to 50°C, respectively. The LC properties of the novel series are compared with two other structurally similar homologous series. The textures of the nematic phase are threaded or schlieren type and those of the smectic phase is of the type A or C. © 2013 Copyright Taylor and Francis Group, LLC.


Patel R.B.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College
Der Pharma Chemica | Year: 2011

The titled new homologous series of twelve mesogens is synthesized by usual established method with, a view to understand and establish the relation between mesogenic properties of the substances and their molecular structure. Methyl to butyl derivatives of the homologous series are nonmesogenic, while pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl and hexadecyl derivatives are enantiotropically mesogenic in character. Pentyl, tetradecyl, hexadecyl derivatives are nematogenic only, while, hexyl to dodecyl derivatives are polymesomorphic i.e. smectic and nematic, both mesophases are exhibited enantiotropically by hexyl to dodecyl homologues. Transitions and melting temperatures of homologues are determined by the polarizing microscope with heating stage. Transition temperatures are plotted versus number of carbon atoms in n-alkyl chain of left n- alkoxy terminal end group. A phase diagram is obtained by joining like points. Solid-mesomorphic or solid-isotropic transition curve initially follows zigzag path of rising and falling upto butyl homologue and then falls gradually upto decyl homologue and again rises steeply to a hexadecyl homologue in a rounded shape from decyl to hexadecyl derivative of the series. Smectic-nematic transition curve, behaves in normal manner and merges solid-mesomorphic / isotropic transition curve at the tetradecyl derivative of homologue, with showing up of odd-even effect. Nematic-isotropic transition curve wonderfully show rising tendency as series is ascended with alternation of transition temperatures, showing odd-even effect. Texture of nematic mesophase is of threaded type and that of smectic mesophase is focal conic fan shaped of the type-A. Analytical data support the structure of the molecules.


Chauhan H.N.,Shri University | Chauhan H.N.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,Jagdishprasad Jhabarmal Tibrewala University
Der Pharma Chemica | Year: 2012

Titled homologous series consists of eleven homologues. Methyl to n-butyl and hexadecyl derivatives are nonliquid crystal while rest of the homologes Viz. n-pentyl to n-tetradecyl derivatives are only enantiotropic nematogenic without exhibition of any smectic character. Odd even effect is observed in nematic-isotropic transition curve. A phase diagram shows that Solid-isotropic or nematic transition curve follows. zigzag path of rising and falling. Nematic-isotropic transition curve behaves in normal manner. Analytical data support the structures of molecules. Texture of nematic mesophase is schlierens or threaded type. Transition and melting temperatures of homologues are determined from hot stage polarising microscope. Liquid Crystal (LC) properties of the series are compared with other structurally similar homologous series. Series is entirly nematogenic with relatively high melting type.


Patel R.B.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College
Der Pharma Chemica | Year: 2011

An ester homologous series entitled Ethyl-p-[p/-n-alkoxy cinnamoyloxy] cinnamates is synthesized and studied for liquid crystal behavior and its correlation with molecular structure. Methyl to n-pentyl homologues are non-liquid crystal while, n-hexyl homologue to n-octyl homologue n-decyl, n-dodecyl, n-tetradecyl and n-hexadecyl homologues exhibit liquid crystal properties especially of enatiotropic nematogenic character, even in the monotropic condition. Transition and melting temperatures (Table-1) are determined by hot stage polarizing microscope. A phase diagram (Figure-I) is obtained by plotting transition temperatures (Table-1) versus number of carbon atoms in n-alkyl chain of left n-alkoxy terminal. Solid-isotropic / nematic transition curve follows zigzag path of rising and falling with overall descending tendency as series is ascended in normal manner. Nematic-isotropic transition curve initially falls from n-hexyl homologue to n-decyl homologue in normal manner and passes through minima at decyl derivative but rises abnormally as series is ascended upto last homologue of series. The texture of the nematogenic mesophase is of threaded type. Analytical data support the structures of the molecules. Nematogenic mesophase length is relatively short with absence of smectic mesophase. Mesomorphic properties are compared with structurally similar homologous series.


Patel R.B.,K K Shah Jarodwala Maninagar Science College | Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College
Der Pharma Chemica | Year: 2011

A new homologous series of nonamphiphilic liquid crystals viz; n-propyl-p-[p'-n-alkoxy cinnamoyloxy] cinnamates with cis confugration is synthesized and studied with a view to understand the effect of molecular structure on mesomorphic properties of substances which may be useful to the various fields of applications. Methyl to pentyl and hexadecyl homologues are nonmesomorphic, hexyl to octyl, decyl, dodecyl and tetradecyl homologues are mesomorphic i.e. nematogenic in character without exhibition of any smectic character. A phase diagram is drawn from the transition temperatures as determined from hot stage polarizing microscope of homologues against the number of carbon atoms in n-alkyl chain of left n-alkoxy terminal end group. Solid-isotropic or solid nematic transition temperature curve follows a zigzag path of rising and falling throughout the series as series is ascended in normal manner. Nematicisotropic transition curve initially rises and then, shows descending tendency as series is ascended. Thus, it follows usual established trend as expected. Wellknown odd-even effect is observed for nematic-isotropic transition curve. Analytical data support the structures of molecules. The enantiotropic nematic mesophase appeared for all the homologues, is of threaded type as determined from miscibility metod. Thermal stability for nematic is 183.80C and mesomorphic range is short which varies from 8.0°C to 27.°C. mesomorphic properties of titled homologous series (1) are compared with structurally similar homologous series (A),(B) and (C).


Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College | Odedara D.A.,M D Science College | Patel R.B.,K K Shah Jarodwala Maninagar Science College
Molecular Crystals and Liquid Crystals | Year: 2012

Three binary systems, each consisting of two nonmesogenic compounds, viz. p-tolual-p-phenetidine (M.P. 108.5C) [A] as the common component, and Methyl p-(p-n-butyloxy benzoyloxy) benzoate (M.P. 119.0C) [B 1], Ethyl-p-(p-n-butyloxy benzoyloxy) benzoate (M.P. 94.0C) [B 2], and n-Butyl p-(p-n-butyloxy benzoyloxy) benzoate (M.P. 130.0C) [B 3] as the second component, respectively, are studied with a view to understand the effect of terminal groups on nematic and/or smectic mesomorphism. Latent transition temperatures (LTT) of the constituent components A, B 1, B 2, and B 3 were determined by extrapolation. Binary system (A + B 1) induces a nematogenic mesophase while binary systems (A + B 2) and (A + B 3) both induce a smectic mesophase in addition to a nematic mesophase. Phase diagrams of the binary systems under investigation are plotted for the mole percent of component (A) versus the transition temperatures of each binary system as determined from polarizing optical microscopy. The texture of the nematic mesophase is of threaded type and that of the smectic mesophase is focal-conic fan shaped of the type smectic-A. Components A, B 1, B 2, and B 3 were prepared by established methods. Analytical data support the structure of molecules under investigation. Melting points of the constituent components match with data reported earlier. © 2012 Copyright Taylor and Francis Group, LLC.

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