In Situ Characterization of Thermal-Induced Evolution of Structure/Optical Properties of Heterogeneous 3D Chiral Soft Photonic Crystal Polymer

Polymer stabilized blue phase (PSBP) liquid crystal has aroused wide attention due to its broad temperature range and potential applications in flexible display, multi-mode monitor, and mirrorless laser based on its well-compatible stability and multi-responsiveness, such as electricity, humidity, and temperature. Temperature produces an important effect on the structure/optical properties of PSBP, but there lack of detailed investigation on thermal-induced deformation and its influence on the optical performance of PSBP. Here, the thermal-induced evolution of structure/optical properties of PSBP with different polymer content is in situ characterized by variable-temperature ultra-small-angle X-ray diffraction, Kossel diffraction, and polarized optical microscopy. A restricted deformation of PSBP cubic lattice is revealed by the shift of reflective wavelength and evolution of Kossel diagrams, which is mainly attributed to the thermal-induced phase transition/separation of non-polymerized components. The thermal stability of PSBP is improved by increased polymer content based on the limited deformation ability. This work is significant for the design of novel functional material, which paves the way for the preparation of photonic crystal soft materials with high stability and optical quality.