Synthesis and alignment of liquid crystalline elastomers

Liquid crystalline elastomers (LCEs) are crosslinked polymer networks that combine the elastic properties of rubber with the anisotropic properties of liquid crystals. Multifunctionality and responsivity can be programmed into LCEs by patterning their local orientation, which is difficult to achieve in other monolithic material systems. Advances in the synthesis and alignment of LCEs have paved the way for their functional integration in robotics, optics, consumer products, energy and healthcare devices. In this Review, we discuss recent advances in materials chemistry and processing that have contributed to the resurgence in LCE research. We examine the mechanical response of LCEs to stimuli and survey approaches for mechanical alignment, surface-enforced alignment, field-induced alignment and rheological alignment. The Review concludes with an over-the-horizon outlook discussing current challenges and emerging research opportunities.