Measurements of ultrasonic velocity V, specific volume v and adiabatic compressibility Kad are carried out in a monotropic nematic liquid crystal, p-anisal-p-phenetidine (pApP), and a polymesomorphic liquid crystal, p-n-decyloxybenzoyl-p-cresol (DBC) with nematic and smectic A phases. Temperature variation of the order parameter is estimated. The pre-transitional effects observed in v and Kad are discussed on the basis of de Gennes' theory generalized by Bendler, and the critical exponents are estimated.
- liquid crystals
- pre-transitional effects
ASJC Scopus subject areas
- Safety, Risk, Reliability and Quality
- Acoustics and Ultrasonics