An In Situ Resonant Soft X-Ray Scattering (RSoXS) Study of a Blue Phase Liquid Crystal Martensitic Transformation

Blue phase liquid crystals can spontaneously form cubic structure with the unit cell a few orders of magnitude larger length scale than the atomic crystal. Directed self-assembly of blue phase liquid crystals (BPLCs) on a chemically patterned surface into arbitrary large area idea single crystal provides us the unique opportunity to observe the martensitic transformation in the soft material system, which further enriches and extends our understanding of such diffusionless phase transformation. Based on the optical crosshatched structure that was previously captured during the phase transition, here, relying on resonant soft X-ray scattering (RSoXS), we conduct a more in-depth quantitative study of such soft crystal martensitic transformation. For the first time, the twin lamella accompanied with the strain release mechanism is found during blue phases transition process, which further proves the martensitic nature in the soft crystal when making an analogy to the classical atomic system. By RSoXS, the collective motion of LC molecules to make the local reorganization of the crystalline array can be easily captured, and such a fundamental understanding of the blue phase transformation will further improve the design of BPLCs based electro-optical devices.<br/><br/>[1] H. M. Jin et al., Soft crystal martensites: An in situ resonant soft x-ray scattering study of a liquid crystal martensitic transformation. Science Advances 6, eaay5986 (2020).