Shear Deformation and Ferroelectricity in Chiral SmC* Main-chain Elastomers

Smart biomimetic micro/nanostructures based on liquid crystal elastomers and networks

A plethora of living organisms are equipped with smart functionalities that are usually rooted in their surface micro/nanostructures or underlying muscle tissues. Inspired by nature, extensive research efforts have been devoted to the development of novel biomimetic functional micro/nanostructured systems. Despite all the accomplishments, the emulation of biological adaptation and stimuli responsive actuation has been a longstanding challenge. The use of liquid crystal elastomers (LCEs) and networks (LCNs) for the fabrication of smart biomimetic micro/nanostructures has recently drawn extensive scientific attention and has become a growing field of research with promising prospects for emerging technologies. In this study, we review the recent progress in this field and portray the current challenges as well as the outlook of this field of research.

Dual relaxation and structural changes under uniaxial strain in main-chain smectic-C liquid crystal elastomer

Relaxation rate of the chevron angle, α becomes about ten times faster at strains exceeding 0.7 than at low strains.

Electrically induced deformation in chiral smectic elastomers with different domain structures

Electrical actuation is investigated in two kinds of chiral smectic liquid-crystal elastomers (LCEs) with different domain structures LCE1 and LCE2: The latter is better than the former in orientational order. Tracking fluorescent beads dispersed on the samples enables us to measure the two-dimensional strain tensors in ferroelectric elastomer films. It turns out that the electric-field-induced strain is polarity dependent and the type of molecular orientation responsible for the strain is specified. In LCE1 the shear strain is dominant, whereas in LCE2 it is comparable to the elongation strain, which is explained by the rotation of the principal axes. The essential differences of the two elastomers are observed in the eigenvalues of the strain tensors. The absolute values for LCE1 are larger than those for LCE2. The difference is discussed on the basis of the domain structures.

Liquid-crystalline elastomer-nanoparticle hybrids with reversible switch of magnetic memory

A stimuli-responsive material is synthesized that combines the actuation potential of liquid-crystalline elastomers with the anisotropic magnetic properties of ellipsoidal iron oxide nanoparticles. The resulting nanocomposite exhibits unique shape-memory features with magnetic information, which can be reversibly stored and erased via parameters typical of soft materials, such as high deformations, low stresses, and liquid-crystalline smectic-isotropic transition temperatures.

Negative Poisson's ratio and semisoft elasticity of smectic-C liquid-crystal elastomers

Models of smectic-C liquid-crystal elastomers predict that they can display soft elasticity, in which the shape of the elastomer changes at no energy cost. The amplitude of the soft mode and the accompanying shears are dependent on the orientation of the layer normal and the director with respect to the stretch axis. We demonstrate that in some geometries the director is forced to rotate perpendicular to the stretch axis, causing lateral expansion of the sample-a negative Poisson's ratio. Current models do not include the effect of imperfections that must be present in the physical sample. We investigate the effect of a simple model of these imperfections on the soft modes in monodomain smectic-C elastomers in a variety of geometries. When stretching parallel to the layer normal (with imposed strain) the elastomer has a negative stiffness once the director starts to rotate. We show that this is a result of the negative Poisson's ratio in this geometry through a simple scalar model.

Measurement of electrically induced shear strain in a chiral smectic liquid-crystal elastomer

The mechanical response to electrical stimulation was investigated in a chiral smectic elastomer. The two-dimensional strain tensor in an elastomer film was precisely measured by tracking fluorescent beads dispersed on the film. Shear deformation in the film was clearly observed when an electric field was applied perpendicular to the film surface. The temperature dependence of the strain tensor was also investigated, and the origin of the electric-field-induced shear strain in the chiral smectic-C phase was mainly attributed to the Nambu-Goldstone mode.