Dithiols as Liquid Crystalline Building Blocks for Smart Polymers via Thiol-yne Click Chemistry

Since 30 years, liquid crystalline elastomers (LCEs) have been attracting the attention of many researchers thanks to their anisotropic molecular structure which allows them to build up artificial muscles. Possible applications span from soft robotics to biomedical or tunable optical devices. The power of thiol-yne click chemistry was recently demonstrated in the preparation of smart polymers, in particular LCEs, in which the mesogenic units are incorporated both in the main-chain and as pendant groups. To enrich the library of available LCE materials, in this work, several liquid crystalline dithiols and alkynes have been synthesized and copolymerized to obtain elastomers with different thermomechanical properties. The architecture of the main chain was found to play a prominent role in modulating the clearing point in a range of 60 °C, whereas only a minor contribution is given by the mesogens in the side chain. On the other hand, the mechanical response resulted highly sensitive to fine details of the side-chain structure. Accordingly, the present study not only improves the basic understanding of the chemical-physical properties of LCEs but paves the way to the preparation of multicomponent actuators able to deform in different temperature ranges, thus ultimately leading to complex soft robotic operations.