Synthesis, Characterization and Phase Transition Studies on Some N-(4-Butyloxy Benzylidene)-4-Alkoxy Anilines, 4O.Om Compounds - A Dilatometric Study

2013 ◽  
Vol 2 (1) ◽  
pp. 38-47
Author(s):  
Venkata Pisipati ◽  
M. Saraswathi ◽  
D. Madhavi Latha ◽  
P. Pardhasaradhi ◽  
P. V. Datta Prasad
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimeter ◽  
Nematic Phase ◽  
The Body ◽  
Transition Temperatures ◽  
First Order ◽  
Dilatometric Study ◽  
Dilatometric Studies ◽  
Transition Studies

Dilatometric studies are carried out on the synthesized N-(4-butyloxy benzylidene)-4-alkoxy anilines, 4O.Om compounds with the m = 3 to 7 and 9. Characterization of these compounds is done using the polarizing microscope attached with a hot stage. The differential scanning calorimeter is employed to find out the transition temperatures as well as the heats of transitions. All the compounds exhibit nematic phase with varying thermal ranges with the clearing temperatures are above 100 OC as unlike the case of the well known N-(4-butyloxy benzylidene)-4-alkyl anilines, 4O.m compounds which exhibit rich poymorphysim and the clearing temperatures are well below 100 OC. As expected the isotropic to nematic transition exhibited first order nature and the results are discussed with the body of the data available in literature.

Smectic C to Nematic Phase Transition Studies in NOBA

1985 ◽  
Vol 40 (5) ◽  
pp. 466-468
Author(s):  
N. V. S. Rao ◽  
V. G. K. M. Pisipati
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Benzoic Acid ◽  
Thermal Expansion Coefficient ◽  
Pressure Dependence ◽  
Nematic Phase ◽  
Clapeyron Equation ◽  
First Order ◽  
Smectic C ◽  
Transition Studies

The variation of density ϱ with temperature of p-n-nonyloxy benzoic acid in its isotropic, nematic and smectic-C phases is presented. The density jumps and the computed thermal expansion coefficient maxima suggest the order of the N - SC and N - I transitions to be first order. The pressure dependence of the transition temperatures as computed from the Clausius- Clapeyron equation and the presence of pretransitional effects at the N - SC and N - I transitions in the nematic phase are discussed.

Dilatometric Study of the Isotropic-Smectic F Transition of 10O.14

1994 ◽  
Vol 49 (4-5) ◽  
pp. 559-562
Author(s):  
N. V. S. Rao ◽  
G. Padmaja Rani ◽  
D. M. Potukuchi ◽  
V. G. K. M. Pisipati
Keyword(s):  
Phase Transition ◽  
Exponential Growth ◽  
Large Temperature ◽  
First Order ◽  
Temperature Range ◽  
Dilatometric Study ◽  
Dilatometric Studies

Abstract The compound N(p-n-decyloxy benzylidene)p-n-tetradecyl aniline, (10O.14), a higher hom ologue of the MBBA series, exhibits smectic F and smectic G phases. Dilatometric studies inferred strong pre-transitional effects in a large temperature range. DSC results confirmed the first order nature of the IF and FG transitions. The exponential growth of continuous six fold hexagonal order across the isotropic-smectic F phase transition is estimated from the density studies with an exponent b = 0.75.

Molecular Ordering in Nematic MBCA and EPAPU

1990 ◽  
Vol 45 (1) ◽  
pp. 29-32
Author(s):  
S. Sreehari Sastry ◽  
V. Venkata Rao ◽  
P. Narayana Murty ◽  
G. Satyanandam ◽  
T. F. Sundar Raj
Keyword(s):  
Phase Transition ◽  
Liquid Crystals ◽  
Order Parameter ◽  
Nematic Phase ◽  
Spin Probe ◽  
Nematic Liquid Crystals ◽  
Experimental Techniques ◽  
First Order ◽  
Molecular Ordering

AbstractBy EPR, two nematic liquid crystals (MBCA and EPAPU) were investigated using a steroidal nitroxide spin probe. In both liquid crystals the isotropic-nematic phase transition is of first order. The observed variation of the order parameter with temperature is compared with predictions from the Maier-Saupe and Humphries-James-Luckhurst models and with results obtained by several other experimental techniques.

Synthesis, characterisation and liquid-crystalline phase transition studies on two higher homologues of 4O.m (m=14 and 16) series

2001 ◽  
Vol 709 ◽  
Author(s):  
C. Rama Chandra Prabhu ◽  
V.G.K.M. Pisipati
Keyword(s):  
Phase Transition ◽  
Liquid Crystalline ◽  
Scanning Calorimetry ◽  
First Order ◽  
Smectic A ◽  
Phase Transition Temperatures ◽  
Crystalline Phase Transition ◽  
M 14 ◽  
Enthalpy Data ◽  
Transition Studies

ABSTRACTThe synthesis, characterization and phase transition studies of higher homologues of N(p-nbutoxybenzylidene)p-n-alkylanilines, Viz., 4O.m series (m=14 and 16) are carried out by thermal microscopy, differential scanning calorimetry and density. The compounds exhibit a phase variant of nematic and smectic-A. Density studies reveal a first order nature of IN transitions and a weak first order NA transitions. An estimate of pressure dependence of the phase transition temperatures using the volume and enthalpy data are presented. A comparison of these results with other reported results in nO.m and other compounds are presented.

scholarly journals Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB–N phase transition

2016 ◽  
Vol 18 (6) ◽  
pp. 4394-4404 ◽  
Author(s):  
D. O. López ◽  
B. Robles-Hernández ◽  
J. Salud ◽  
M. R. de la Fuente ◽  
N. Sebastián ◽  
...  
Keyword(s):  
Field Theory ◽  
Experimental Data ◽  
Phase Transition ◽  
Liquid Crystal ◽  
Nematic Phase ◽  
Mean Field Theory ◽  
Mean Field ◽  
Landau Model ◽  
First Order ◽  
Miscibility Studies

We have developed a Landau model that predicts a first order twist-bend nematic–nematic phase transition.

Phase Transition Studies in PMBAB and PEBAB

1984 ◽  
Vol 39 (7) ◽  
pp. 696-699 ◽  
Author(s):  
V. G. K. M. Pisipati ◽  
N. V. S. Rao
Keyword(s):  
Phase Transition ◽  
Thermal Expansion ◽  
Molar Volume ◽  
Ultrasonic Velocity ◽  
Adiabatic Compressibility ◽  
First Order ◽  
Thermal Expansion Coefficients ◽  
Methylene Unit ◽  
Expansion Coefficients ◽  
Transition Studies

The variation of density and ultrasonic velocity with temperature in N-(p-methoxybenzylidene)- p-aminobenzonitrile (PMBAB) and N-(p-ethoxybenzylidene)-p-aminobenzonitrile (PEBAB) are presented. The density jumps and thermal expansion coefficients suggest the nematic-isotropic transition of both compounds to be of first order. The adiabatic compressibility βad, molar sound velocity Rn and molar compressibility Aw are computed. The contribution of a methylene unit to the molar volume is found to be higher than literature values. The anomalous ultrasonic velocity dip at the nematic-isotropic transition for both compounds is found to be high; the value is many times those found for other nematic-isotropic or nematicsmectic A transitions.

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