A side chain mesomorphic co-oligomer possesses a large blue-phase temperature domain. Upon cooling down from blue phase I colored crystallites are quenched below the glass transition of this material. The microtome cut of these crystallities and their observation by transmission electron microsocopy reveal the presence of biperiodic textures different from the cholesteric ones. Image analysis of these textures, associated with an original model of diffraction confirms the presence of the ${\mathit{O}}^{8\mathrm{-}}$ symmetry and suggests that the transmission electron microscopy contrast obtained here has to be associated with changes of the molecular orientations in the bulk of the sample.

• Received 1 May 1992

DOI:https://doi.org/10.1103/PhysRevLett.69.2935