A.V.Glushchenko, V.S.Sperkach, O.V.Yaroshchuk Sound propagation in liquid crystal 5CB and 5CB based aerosil suspensions |
Acoustic bulletin, Vol. 3 ¹ 3, (2000) |
| The sound speed and absorption in nematic liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) and its mixtures with aerosil within the temperatures of nematic and isotropic phases of 5CB are investigated. In both pure 5CB and its mixtures with aerosil the two relaxation regions with frequencies fr1≈10 MHz and fr2≈400 MHz are revealed. The relaxation frequency fr1 critically increases in the nematic-isotropic phase transition and decreases with the increase of the aerosil concentration. Simultaneously, the frequency fr2 does not demonstrate critical behaviour in the transition region and practically does not change at the insetion of aerosil dopant. It is beleaved, that the first relaxation region is connected with the peculiarities of mesomorphic state, whereas the second one is typical for all liquids. A linear increase of the absorption coefficient and monotonous decrease of the sound velocity at the increasing of aerosil concentration reflect the constitution of aerosil in form of separated aggregates and lack of three-dimensional aerosil network. |
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KEY WORDS: liquid crystals, sound speed, absorption coefficient, relaxation region |
| TEXT LANGUAGE: Ukrainian |