Propagation of acoustic waves in nematic elastomers

Abstract

We develop a theory of elastic waves in oriented monodomain nematic elastomers. The effect of soft elasticity, combined with the Leslie-Ericksen version of dissipation function, results in an unusual dispersion and anomalous anisotropy of shear acoustic waves. A characteristic time scale of nematic rotation determines the crossover frequency, below which waves of some polarizations have a very strong attenuation while others experience no dissipation at all. We study the anisotropy of low-frequency Poynting vectors and wave fronts, and discuss a "squeeze" effect of energy transfer nonparallel to the wave vector. Based on these theoretical results, an application, the acoustic polarizer, is proposed.

Effective high-order approximations of layered coatings and linings of anisotropic elastic, viscoelastic and nematic materials

“…For a single-layer coating and lining of nematic material (Ne) we took the following values of the parameters: [31][32][33] (or D 2 2 /(4D 1 ) = g 44 , which is called an ideal case, since, according to relations (5.4) g R 44 (0) = 0, ... it corresponds more to the behaviour of a liquid crystal). The values g 11 , g 12 , g 13 , g 33 are close due to the high bulk compression modulus.…”

Dynamics, dynamic soft elasticity, and rheology of smectic-Celastomers

“…At non-vanishing frequency the system cannot be ideally soft but it can be nearly so for ω small. This type of behavior was first predicted for nematic elastomers, where it has been termed dynamic soft elasticity [9]. The storage moduli for u xy and u yz strains, Eq.…”

“…In the y ′ z ′ and x ′ z ′ -planes, their velocities are non-vanishing in all directions. Note that, since the velocity of pair (i) vanishes in directions where the velocities of the other modes remain finite, SmC elastomers are, like nematic elasomers [9], potential candidates for applications in acoustic polarizers.…”

“…One consequence of Eq. (9) is that SmC elastomers could exhibit so-called dynamic soft elasticity [9]. To highlight this phenomenon, let us switch briefly to the rotated reference space coordinates x ′ , y ′ , z ′ .…”

“…(9), in the original coordinate system are nonzero at zero frequency. Their behavior for ω > 0, like that of semi-soft nematic elastomers [5,9], depends on τ n /τ E . If τ n ≫ τ E , the storage moduli exhibit a step and the corresponding loss moduli an associated peak at ωτ n ∼ 1 as shown in Fig.…”