Stretchable Freestanding Films of 3D Nanocrystalline Blue Phase Elastomer and Their Tunable Applications

Given that it is a potential medium for 3D manipulation of photons in the forward‐looking technology of quantum optics, nonlinear optics, electronics, nanomaterials, and bionics, 3D photonic crystal (PhC) is a promising material of strategic significance and has great impact on scientific development. Blue phase (BP), a liquid crystalline mesophase with unique nanoscaled 3D PhC features, has been shown to contain significant potential values in fundamental studies and technological applications. However, thus far, the environmental stability of BP devices remains a puzzling issue of material exploitation. Therefore, in this study, stretching‐tunable BP elastomer (BPE) photonic bandgap (PBG) free‐standing films are fabricated via full photopolymerization. The BPE films exhibit benefit‐specific features, including sharp PBG with high reflectivity and flexible tunability in the visible region, high thermal stability, and good mechanical ductility and resistance in chemicals. These properties are attributed to the pre‐developed, fully‐reactive mesogenic materials employed, which show BP states in a wide temperature range, including room temperature. Additionally, mirrorless laser applications with flexible tunability are also realized in this study. The freestanding BPE film can be used as a prototype instrumentality to promote the future development of multifunctional intelligent applications in lasers, sensors, displays, intelligent lightings, lidars, micro‐robots and antennas. A flexible and stretching‐tunable blue phase elastomer (BPE) photonic bandgap (PBG) freestanding film and a mirrorless laser are made by fully reactive mesogenic materials at room temperature. The BPE film with a well‐defined 3D nanocrystalline superstructure formed by self‐assembly shows sharp PBG, high reflectivity and tunability in the visible region, high thermal stability, good mechanical ductility, and high chemical resistance.