Results of Ultrasonic Velocity and Density Investigations of the Nematic Liquid Crystal

• Autorzy: Balcerzak A.
• Języki publikacji: EN

Abstrakty

EN

Velocity of ultrasonic longitudinal waves in the nematic liquid crystal 1-(trans-4- hexylcyclohexyl)-4-isothiocyanatobenzene (6CHBT) has been measured as a function of temperature between 24oC and 55oC at 5.2 MHz. The temperature dependence of velocity shows a local minimum in the region of the nematicisotropic (N-I) phase transition. Additional temperature measurements of density have been done to calculate the thermal coefficient of expansion and the temperature coefficient of adiabatic compressibility. Both these parameters exhibit critical behaviour at the transition which has been analysed. The values of the exponent determining the growth of the order fluctuations have been calculated and compared with references.

Słowa kluczowe

EN

liquid crystal; ultrasonic velocity; nematic-isotropic transition

• Wydawca: Silesian Division of Polish Acoustical Society
• Czasopismo: Molecular and Quantum Acoustics
• Rocznik: 2004
• Tom: Vol. 25
• Strony: 17--22
• Opis fizyczny: Bibliogr. 7 poz., rys.

Twórcy

autor

Balcerzak A.

• Institute of Fundamental Technological Research, Polish Academy of Sciences, Świętokrzyska 21, 00-049 Warszawa, Poland,

Bibliografia

• 1. P.G. de Gennes, J. Prost, Physics of liquid crystals, Claredon Press, Oxford 1998.
• 2. Y. Kawamura, Y. Maeda, K. Okano, S, Iwayanagi, “Anomalous ultrasonic absorption and dispersion of nematic liquid crystals near the clearing point”, Jap.J.Appl.Phys., 12, 1510- 1521 (1973).
• 3. Y.V. Sperkach, V.S. Sperkach, O. Aliokhin, A.L. Strybulevych, M. Masuko, “Temperature dependence of acoustical relaxation times involving the vicinity of N-I phase transition point in 5CB liquid crystal”, Mol.Cryst, and Liq.Cryst, 366. 183-202 (2001).
• 4. G.G. Natale, “The contribution of ultrasonic measurements to the study of liquid crystals. I. Nematics”, J.Acoust.Soc.Am., 63,1250-1278 (1978).
• 5. A.K. George, “On critical phenomena in liquid crystals”, Acustica, 73,287-290 (1991).
• 6. A. Balcerzak, “Temperature dependencies of ultrasonic absorption and velocity in the 1- (fraflS'4-hexylcyclohexyl)-4-isothiocyanatobenzene”, Proceedings LI Open Acoustic Seminar, Gdansk - Sobieszewo 2004 [in Polish],
• 7. P.H, Keyes, J.R. Shane, “Tricritical exponents for the isotropic-nematic transition: an experimental verification”, Phys.Rev.Lett. 42,722-725 (1979).