DYNAMICS OF BLUE-PHASE SELECTIVE REFLECTIONS IN AN ELECTRIC-FIELD

Electric fields can cause structural changes of the blue phases (BP) that appears in chiral liquid crystals. In BP I and BP II, electrostrictive effects cause a shift of the Bragg reflection wavelengths with little intensity change. In BP III, for systems with negative dielectric anisotropy, there is a strong increase in the selective reflection intensity in addition to electrostriction. We have measured the time response of these effects to on-off modulated electric fields for a material with negative dielectric anisotropy. We observe that the response times for BP I and BP II electrostriction are 10 s, while the response times for BP III peak intensification are 10 ms. We discuss the results in terms of models for these mechanisms and the as yet unknown structure of BP III. © 1990 The American Physical Society.