scholarly journals Phase Transition Studies in Polymesomorphic Compounds II. Ultrasonic Velocity Studies in N(p-n-Heptyloxy Benzylidene)p-n-Butyl Aniline

1982 ◽  
Vol 37 (11) ◽  
pp. 1262-1265
Author(s):  
V. G. K. M. Pisipati ◽  
N. V. S. Rao
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Sound Velocity ◽  
Ultrasonic Velocity ◽  
Adiabatic Compressibility ◽  
First Order ◽  
Smectic A ◽  
Smectic C ◽  
Good Agreement ◽  
Transition Studies

The variation of ultrasonic velocity in N (p-n-heptyloxy benzylidene)p-n-butyl aniline, (HyBBA) with temperature in isotropic, nematic, smectic-A, smectic-C and smectic-G phases is measured. All the phase transitions I-N, N-SA, SA-SC and SC-SG are found to be of first order. The adiabatic compressibility βad, molar sound velocity or Rao number Rn, and molar compressibility or Wada constant AW are computed. Rn and AW of HyBBA are compared with theoretical values and found to be in good agreement with the theory.

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.

Phase Transition Studies across Isotropic-Smectic A and Smectic A-Smectic F Phases in 90.4

1989 ◽  
Vol 44 (1) ◽  
pp. 23-25
Author(s):  
D. M. Potukuchi ◽  
P. Bhaskara Rao ◽  
N. V. S. Rao ◽  
V.G. K. M. Pisipati
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Thermal Expansion ◽  
Phase Transitions ◽  
Pressure Dependence ◽  
Scanning Calorimetry ◽  
First Order ◽  
Smectic A ◽  
Density Results ◽  
Transition Studies

Abstract The temperature dependence of the density of N(p-n-nonyloxy benzylidene)p-n-butylaniline (90.4) is studied. The compound exhibits smectic A, smectic F and smetic G phases. The isotropicsmectic A (IA) and smetic A-smectic F phase transitions are found to be first order. The calculated thermal expansion coefficient and differential scanning calorimetry support the density results. The density jumps, associated enthalpies and the estimated pressure dependence of the transition temperatures for IA transitions in other compounds are also presented.

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.

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.

Destruction of a first-order smectic-A→smectic-C*phase transition by dimensional crossover in free-standing films

1993 ◽  
Vol 48 (3) ◽  
pp. 1916-1923 ◽  
Author(s):  
Isabelle Kraus ◽  
Pawel Pieranski ◽  
Evgenij Demikhov ◽  
Horst Stegemeyer ◽  
John Goodby
Keyword(s):  
Phase Transition ◽  
Dimensional Crossover ◽  
Free Standing ◽  
First Order ◽  
Smectic A ◽  
Smectic C

Density, Refractive Index and Ultrasonic Velocity Studies Involving N-(p-n-Pentyloxybenzylidene)-p-n-octylaniline

1985 ◽  
Vol 40 (5) ◽  
pp. 472-475 ◽  
Author(s):  
V. G. K. M. Pisipati ◽  
N. V. S. Rao ◽  
P. V. Datta Prasad ◽  
P. R. Alapati
Keyword(s):  
Refractive Index ◽  
Ultrasonic Velocity ◽  
Adiabatic Compressibility ◽  
Isotropic Liquid ◽  
First Order ◽  
Smectic A ◽  
Liquid Phases ◽  
First Order Transition ◽  
Nematic Phases ◽  
Enthalpy Data

The density, refractive index and ultrasonic velocity dependence on temperature for N-(p-npentyloxybenzylidene)- p-n-octylaniline, 50.8, is presented. The compound 50.8 exhibits smectic-B, smectic-A and nematic phases between the solid and isotropic liquid phases. The nematic-isotropic and smectic A-smectic B phase transformations are found to be first order. The interesting smectic A - nematic transformation is confirmed from the results to be second order, although the thermal expansion coefficient and reported enthalpy data had suggested a weak first order transition. The computed adiabatic compressibility, βad, molar sound velocity, Rn, and molar compressibility Aw are presented.

TRICRITICAL BEHAVIOR AT THE SMECTIC-A-SMECTIC-${\rm C}^{*}_{\alpha}$ PHASE TRANSITION

2007 ◽  
Vol 21 (23) ◽  
pp. 1579-1584 ◽  
Author(s):  
PRABIR K. MUKHERJEE
Keyword(s):  
Phase Transition ◽  
Electric Field ◽  
Tricritical Point ◽  
Phenomenological Approach ◽  
Alpha Phase ◽  
Electric Field Effect ◽  
First Order ◽  
Smectic A ◽  
Tricritical Behavior ◽  
Good Agreement

A simple phenomenological approach to the description of the electric field effect on the Smectic-A-Smectic-[Formula: see text] phase is discussed. It is shown that with a particular value of the electric field E tcp the second-order Smectic-A-Smectic-[Formula: see text] phase transition (no field) becomes first order at a tricritical point. The results are in good agreement with recent experiments.

scholarly journals INFLUENCE OF PRESSURE ON SMECTIC A-NEMATIC PHASE TRANSITION

1999 ◽  
Vol 13 (09n10) ◽  
pp. 275-283 ◽  
Author(s):  
KISOR MUKHOPADHYAY ◽  
PRABIR K. MUKHERJEE
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Phenomenological Model ◽  
Order Parameter ◽  
Nematic Phase ◽  
Tricritical Point ◽  
Second Order ◽  
Experimental Results ◽  
First Order ◽  
Smectic A

We propose a Landau-de Gennes phenomenological model to describe the pressure induced smectic A-nematic phase transition. The influence of pressure on smectic A-nematic phase transitions are discussed for varying coupling between orientational and translational order parameter with pressure. Increasing the pressure, the first order nematic-smectic A transition becomes second order at a tricritical point which agrees fairly well with available experimental results.

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