Ferroelectric liquid‐crystalline elastomers

Abstract

Oriented liquid-crystalline (LC) elastomers (polar monodomains, concerning the direction of polarisation) have been prepared from polar monodomains of ferroelectric LC-polysiloxanes by a radical photocrosslinking process. Attempts to perform ferroelectric switching lead in these soft elastomers to an elastic stress which prohibitsfor low voltagesa complete reorientation of the polar axis (ferroelectric switching). A ferroelectric switching can, however, be observed for high voltages. The loop of hysteresis of this switching is asymmetric concerning the zero point of the driving voltage. Piezoelectric measurements show that these elastomers combine an elastic memory for one polar state with enough flexibility to allow a reorientation of the polar axis.

Ferroelectric liquid crystalline elastomers, 1. Variation of network topology and orientation

“…Previous studies on the elastomers of terpolymer P2 show a successful stabilization of one ferroelectric switching state, when the crosslinking reaction takes place in the smectic-C* phase with applied d.c.-field 11,12) . Afterwards a switching of the mesogens in the second, unfavored switching-state is still possible.…”

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

“…Various methods of alignment are used to obtain single-crystal monodomains, which ensure these elements act together. Shearing surface force [44], electrical [180] and magnetic fields [61] are all well-known methods for aligning mesogens before initiating polymerisation to preserve this orientation. Photoalignment can create spatially varying responses in two dimensions, demonstrated both continuously [181,182] and using a discrete voxel approach [60].…”

Elastic Properties of Liquid Crystal Elastomer Balloons

“…The formation of an elastic network leaves the phase sequences and many anisotropic properties nearly unaffected, but it introduces a coupling between the orientation of the mesogens and macroscopic elastic deformations of the network. Ferroelectric smectic phases, due to their strong interactions with electric fields, open the possibility to switch the mesogenic orientation even in presence of the network [2]. A typical ferroelectric hysteresis can be measured.…”

“…A typical ferroelectric hysteresis can be measured. It has been shown that the switching properties of ferroelectric LCE depend strongly on the network topology [2,3]. The dynamics and mechanical properties of ferroelectric LCE have been investigated with various experimental methods, for example with dielectric spectroscopy [6] Michelson-interferometry [4], Fourier transform IR [5] and AFM [7].…”