Director configuration in the twist-bend nematic phase of CB11CB

The director distribution in the nematic phases exhibited by the 1′′,11′′-bis(4-cyanobiphenyl-4′-yl)undecane (CB11CB) liquid crystal has been studied in the bulk using the EPR spin probe technique. EPR spectra confirmed the presence of a higher temperature uniaxial nematic phase and of a lower temperature nematic phase in which the director distribution is not uniform. Spectra recorded in the lower temperature nematic phase were not fully compatible with theoretical EPR spectra calculated according to the recently proposed model for the twist-bend phase in which the local domain director twists around an axis with a fixed tilt angle, 0 , but were well described by a "distributed-tilt" model in which the director has a relatively narrow distribution, centred at 0 . Detailed EPR spectral analyses suggest a distributed rather than a fixed tilt angle in the twist-bend nematic phase.