Liquid crystalline elastomers as artificial muscles

New nematic co-elastomers were synthesized which consist of a combination of nematic side- and main-chain polymers and where the liquid crystalline main-chain polymer can be considered as a macromolecular crosslinking component. By applying a mechanical field during the crosslinking process, the director of the nematic phase becomes macroscopically uniformly aligned and liquid-single-crystal elastomers were obtained. Within a narrow temperature regime, these networks can change their shape in one dimension by a factor > 3 and considerably improve the ability of being used as artificial muscles or mechanical actuators compared to the well known nematic side-chain elastomers. Networks having a non-ordered polydomain structure exhibit “soft (or semi-soft) elasticity” which is not only determined by a director reorientation process. Obviously, hairpin conformations within the main-chain segments contribute to this effect.