EPR Study of the Polydomain Structure of the Twist-Bend Nematic Phase of CB9CB in the Bulk

EPR spin probe spectra of the liquid crystal phases exhibited, in the bulk, by the 1 '', 9 ''-bis(4-cyanobiphenyl- 4'-yl) nonane (CB9CB) bent-shape dimer showed that, on cooling from the isotropic phase, this material forms a uniaxial nematic phase with a uniform director macroscopically aligned along the spectrometer field. Upon further cooling, a transition into the twist-bend nematic phase is observed after a biphasic region of approximately 4 K. In this lower temperature nematic phase, the director does not appear to be macroscopically aligned. The non-uniform director distribution is modelled as a collection of monodomains tilted with respect to the magnetic field and orientationally distributed around the tilt direction. [GRAPHICS] .