TY - JOUR
T1 - INVESTIGATION OF ULTRASONIC VELOCITY AND RELATED PARAMETERS IN LIQUID CRYSTALLINE MIXTURES.
AU - George, A. K.
AU - Vora, R. A.
AU - Padmini, A. R.K.L.
PY - 1980
Y1 - 1980
N2 - Investigations of ultrasonic velocity, specific volume and related parameters were carried out in a mixture of p-n-butoxybenzylidene-p-chloroaniline (BBCA) and p-anisal-p-toluidine (pApT) at eight different concentrations. BBCA exhibits polymorphism with two smectic phases, viz. , smectic B and smectic A, while pApT is non-mesomorphic. All the mixtures studied were nematic, the mesomorphism vanishes below 34. 3 mole percent of BBCA. Specific volume showed a large increase in the vicinity of the phase transition and the ultrasonic velocity showed an abrupt minimum near the transition. The adiabatic compressibility showed a maximum near the phase transition. It was found that the dip in ultrasonic velocity, change in specific volume and the jump in adiabatic compressibility at the transition decreases with increasing concentration of the nonmesomorphic compound. The parameter, viz. , molar sound velocity was also estimated. The coefficient of thermal expansion and adiabatic compressibility were also estimated and they were found to attain very high values near the phase transition. The experimental results are explained on the basis of de Gennes theory of pre-transitional effects generalized by Bendler. The critical exponents are estimated in the isotropic as well as in the nematic phases.
AB - Investigations of ultrasonic velocity, specific volume and related parameters were carried out in a mixture of p-n-butoxybenzylidene-p-chloroaniline (BBCA) and p-anisal-p-toluidine (pApT) at eight different concentrations. BBCA exhibits polymorphism with two smectic phases, viz. , smectic B and smectic A, while pApT is non-mesomorphic. All the mixtures studied were nematic, the mesomorphism vanishes below 34. 3 mole percent of BBCA. Specific volume showed a large increase in the vicinity of the phase transition and the ultrasonic velocity showed an abrupt minimum near the transition. The adiabatic compressibility showed a maximum near the phase transition. It was found that the dip in ultrasonic velocity, change in specific volume and the jump in adiabatic compressibility at the transition decreases with increasing concentration of the nonmesomorphic compound. The parameter, viz. , molar sound velocity was also estimated. The coefficient of thermal expansion and adiabatic compressibility were also estimated and they were found to attain very high values near the phase transition. The experimental results are explained on the basis of de Gennes theory of pre-transitional effects generalized by Bendler. The critical exponents are estimated in the isotropic as well as in the nematic phases.
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U2 - 10.1080/00268948008071439
DO - 10.1080/00268948008071439
M3 - Article
AN - SCOPUS:0019267238
SN - 0026-8941
VL - 60
SP - 297
EP - 310
JO - Molecular Crystals and Liquid Crystals
JF - Molecular Crystals and Liquid Crystals
IS - 4
ER -