Entity

Time filter

Source Type


Chauhan B.C.,P.A. College | Doshi A.A.,M. S. University of Baroda | Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College
Molecular Crystals and Liquid Crystals | Year: 2013

The synthesis and mesomorphic properties of a new homologous series of azomesogens, 4-(4′-n-alkoxy benzoyloxy)-3-methoxy phenyl azo-3″,4″ dichlorobenzene is detailed. The first four members of the series are nonmesomorphic, and the other eight members are smectogenic in character. The smectic mesophase, which is exhibited montropically, commences from the pentyl to the hexadecyl derivatives. The usual odd-even effect is observed in the isotropic-smectic transition curve. The isotropic-smectic transition curve behaves in a normal manner. The smectic mesophase shows a focal conic fan shaped texture of the smectic A type. An important feature of the series is the absence of the nematic property. The thermal stability and mesomorphic characteristic are compared with two structurally similar homologous series. © 2013 Copyright Taylor and Francis Group, LLC. Source


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

Ester homologous series of mesogens of cis configuration viz. n-Hexyl-p-(-p /-n-alkoxy cinnamoyloxy) cinnamates is synthesized and studied to understand and establish the relation between the molecular structure and mesogenic properties. Twelve homologues are synthesized. Methyl and ethyl derivatives of homologues are nonmesogenic while, n-propyl to n-octyl, n-decyl, n-dodecyl, n-tetradecyl and nhexadecyl derivatives of the homologues are enantiotropically nematogenic in nature. Enantiotropic smectogenic character commences from heptyloxy derivative and end to tetradecyl homologue. Smectic mesophase is absent in hexadecyloxy homologue. Transition temperatures and melting temperatures of homologues are observed through hot stage polarizing microscope. A phase diagram obtained from transition temperatures of homologues. The solid-isotropic/mesomorphic transition curve adopt a zigzag path of rising and falling tendency in normal manner. Smectic-nematic transition curve rises from nheptyloxy homologue and exhibit falling tendency up to tetradecyloxy homologue and behaves in normal manner without odd-even effect. Nematic-isotropic transition curve initially rises from propyloxy homologue and passes through a maxima at the octyloxy homologue and then smoothly falls to the hexadecyl homologue with exhibition of odd-even effect. Thus nematic-isotropic transition curve behaves in usual manner. The texture of the nematic mesophase is of focal conic fan or batonnate shaped. Analytical data support the molecular structure of homologues. Thus, series is predominantly nematogenic and partly smectogenic in enantiotropic manner. Source


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. Source


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

Homologous series p-(p/-n-alkoxy Cinnamoyloxy) β-benzoyl Styrene is synthesized and studied with a view to understand and to established the relation between molecular structure and liquid crystal property. Homologues are synthesized by reacting p-n-alkoxy cinnamoyl chlorides with p-hydroxy β-benzoyl styrene. Totally twelve homologues are synthesized. Methyl to pentyl homologues are nonmesomorphic while, hexyl to octyl, decyl, dodecyl, tetradecyl and hexadecyl homologues are only nematogenic without exhibition of any smectogenic character even in the monotropic condition. Transition temperatures of the homologues are determined from hot stage polarizing microscope. Solid-isotropic / nematic transition curve in a phase diagram follows a zigzag path of rising and falling and shows overall falling tendency as series is ascended in usual manner. Nematic-isotropic transition curve adopt a descending tendency as series is ascended and behaves in normal manner without showing up of odd-even effect. Melting temperatures are varied between 104.0° C and 179.0° C. Mesomorphic range and nematicisotropic thermal stability are 6.0° Cto 47.0° C and 144.5° C respectively. Analytical data support the structures of molecules. The texture of nematic mesophase is of threaded type as determined by miscibility method. Thus, series under investigation is entirely nematogenic with middle ordered melting type and short range of liquid crystallinity. Mesomorphic properties are compared with structurally similar other homologous series. Source


Bhoya U.C.,Gujarat University | Doshi A.V.,Matushri Virbaima Mahila Science and Home Science College
Der Pharma Chemica | Year: 2011

A homologous series with -COO- and -N=N-, as central groups have been synthesized by treating p-n-alkoxy benzoyl chlorides with p-methoxy -p/-hydroxy azobenzene. All the homologues of the series are mesomorphic in nature. The nematic type mesophase commences from the very first member of the series. Polymesomorphism is exhibited by tetradecyl homologue i.e. smectic and nematic mesophases appear, one after another. Hexadecyl member is purely smectogenic. On plotting transition temperatures versus number of carbon atoms in nalkyl chain of left n- alkoxy terminal, a phase diagram is obtained. Solid-isotropic /mesomorphic transition curve, shows usual zigzag path of rising and falling. Nematic-isotropic and smectic - isotropic transition curves behave in normal manner with and without odd-even effect respectively. The series is high melting type with considerable mesomorphic range. Thermal stability and other mesogenic properties are comparable with structurally similar known series. Analytical data support the structure. Transition temperatures are determined by hot stage polarizing microscope. Texture of nematic and smectic mesophases confirmed by miscibility method. Nematic mesophase is of threaded type and that of smectic mesophase are focal conic fan shaped of type smectic-A for tetradecyl and smectic-C for hexadecyl homologue. Source

Discover hidden collaborations