Biomedical subjects

EM Terentjev

Publications and source records attributed to EM Terentjev.

14 recordsLinked to original sources

PubMed2000

Untwisting of a cholesteric elastomer by a mechanical field

A mechanical strain field applied to a monodomain cholesteric elastomer will unwind the helical director distribution. There are similarities with the classical problem of an electric field applied to a cholesteric liquid crystal but also differences. Frank elasticity is of minor importance unless the gel is very weak. The interplay is between the director being helically anchored to the rubber elastic matrix and the external mechanical field. Stretching perpendicular to the helix axis induces the uniform unwound state via the elimination of sharp, pinned twist walls above a critical strain. Unwinding through conical director states occurs when the elastomer is stretched along the helical axis.

Journal Article↗

PubMed2000

Colloid-liquid-crystal composites: An unusual soft solid

Mixing model colloidal particles with a thermotropic nematic liquid crystal results in a soft solid with significant storage modulus (G' approximately 10(3)-10(5) Pa). The soft solid comprises a network of particle aggregates, formed by the exclusion of particles from emergent nematic domains as the mixture is cooled below the isotropic-nematic transition. The unusually high storage modulus of the colloid-liquid-crystal composites may be due to the local frustration of nematic order within the particle aggregates. The birefringent soft solid is potentially important as a switchable electro-optical material that can be readily handled and processed.

Journal Article↗

PubMed2000

Elasticity of rubber with smectic microstructure

Using a physically motivated continuum model for the free energy of an elastomer with a smectic or lamellar microstructure, we examine the effects of coupling between the smectic and the rubber-elastic degrees of freedom on measurements of the layer structure and elastic moduli. In agreement with experiment, we find that the elastic response to stretching along the layer normal is greatly increased by the smectic layering, while the modulus parallel to the layers is unchanged. We show that Landau-Peierls instability of fluctuations in the layer structure of ordinary smectic liquid crystals is removed by the elastic matrix. Consequently one sees Bragg peaks in the diffraction pattern of a solid with one-dimensional order and we calculate the Debye-Waller factors for these.

Journal Article↗

PubMed1998

Texture Evolution during the Polydomain-Monodomain Transition in Nematic Elastomers.

We have studied the behavior of a liquid crystalline elastomer undergoing a polydomain-monodomain transition. The textures emerging under increasing extensional load have been examined with a combination of optical microscopy, X-ray, and small-angle polarized light scattering. The experimental data are interpreted in terms of reorientation of the local director with increasing extension. The results of this combination of techniques at low extensions are consistent with a two-dimensionally periodic director texture. The amplitude of this modulation decreases continuously as the mesogens are pulled into the extensional direction at high loads. In this manner the samples which are polydomain under no load become essentially monodomain with increasing extension.

Journal Article↗

PubMed1996