Liquid crystal elastomer shell actuators with negative order parameter.

Liquid crystals (LCs) are nonsolids with long-range orientational order, described by a scalar order parameter 〈 P 2 〉 = 1 2 〈 3 cos 2 β - 1 〉 . Despite the vast set of existing LC materials, one-third of the order parameter value range, -1/2 < 〈P 2〉 < 0, has until now been inaccessible. Here, we present the first material with negative LC order parameter in its ground state, in the form of elastomeric shells. The optical and actuation characteristics are opposite to those of conventional LC elastomers (LCEs). This novel class of anti-ordered elastomers gives access to the previously secluded range of liquid crystallinity with 〈P 2〉 < 0, providing new challenges for soft matter physics and adding a complementary type of LCE actuator that is attractive for applications in, e.g., soft robotics.