Highly Efficient Elastomeric Fluorescence Sensors for Force Detection

Carbazole-containing nematic liquid single crystal elastomers (LSCEs) alter their luminescence upon the application of an external mechanical force. Therefore, they are valuable flexible materials for detecting mechanical events with simple fluorescent measurements. In this work, we have focused our attention on the main principles underlying the operation of these materials and the development of novel design schemes to produce efficient elastomeric fluorescence sensors for force detection. In this context, comprehending and controlling the interactions established between the distinct components of the active material, i.e., mesogens and fluorophores, is essential to achieving force-sensitive materials with improved performances. With this purpose in mind, we have explored the role of two structural features on such phenomenon, namely, the type of connection (end-on or side-on) of the carbazole fluorophores to the elastomeric network and the length of the alkyl chain that binds them to the main polysiloxane backbone. As a whole, end-on carbazole fluorophores with short or medium flexible spacers enable a much better approximation to the mesogenic moieties upon deformation, promoting quenching and resulting in more efficient force sensors.