Liquid‐crystalline main‐chain elastomers

Abstract

A main-chain elastomer was synthesized for the first time by a cross-linking hydrosilylation of a cyclosiloxane with a new main-chain liquid crystalline semiflexible polyether. Imposing a uniaxial mechanical field to the unstretched nematic polydomain sample results in a macroscopic alignment of the director. For this process the sample has to be stretched by a factor of about 5, which considerably exceeds the effect observed for nematic side-chain elastomers.

Monodomain Liquid Crystal Main Chain Elastomers by Photocrosslinking

“…For monodomains of these systems large strain thermal actuation has been demonstrated, drastically exceeding the effects found for side chain elastomers. Up to now, different synthetic routes to MC-LCEs have been proposed, including either polyaddition reactions (hydrosilylation, epoxyresins) for the in situ formation of the network [7][8][9][10] or the use of thermoplastic, selforganizing triblock copolymers. [11,12] By applying uniaxial stress during the formation of the network, monodomains of the elastomers could be prepared.…”

“…[1][2][3][4][5] For side chain LC elastomers (SC-LCE), where the mesogens are attached as side groups to a polymer backbone, a lot of work has been done on both nematic and smectic systems. [6] Recently main chain LC elastomers (MC-LCE), in which the mesogens are directly incorporated into the polymer backbone, have also attracted more attention, [7][8][9] due to the direct coupling of the liquid crystalline order and the polymer backbone conformation. For monodomains of these systems large strain thermal actuation has been demonstrated, drastically exceeding the effects found for side chain elastomers.…”

Monitoring the Contractile Properties of Optically Patterned Liquid Crystal Based Elastomers

“…In his studies on reticulated liquid crystal polymers, he mentioned the possibility of the material deformation without constraint. In 1981 Frinkelmann et al have realized the first mesomorphic oriented side-chain LCE [26] and afterwards the first main-chain LCE was synthesized by Bergmann et al [27]. Indeed, according to the insertion topology of the mesogen (liquid crystal phase-forming unit) in the elastomer, there exist two main families of LCEs: side-chain and main-chain elastomers.…”

Synthesis and structure of polysiloxane liquid crystalline elastomers with a mesogenic crosslinking agent

“…1,[5][6][7][8][9]13,[15][16][17][18] In addition, LCEs were extended to crosslinked side-chain liquid crystal polymers with polyacrylate and polymethacrylate backbones 14,19 -26 and also to slightly crosslinked main-chain polymers and combined polymers. 19,[27][28][29][30] These elastomers, prepared by a one-or two-step process in which monofunctional liquid crystal monomers and bifunctional crosslinking agents, such as divinyl derivatives, were simultaneously or successively attached to the polymer backbone. The chemical composition of the LCEs, besides the crosslinking unit, is similar.…”