Proton-decoupled deuterium NMR study of an asymmetric liquid crystal dimer having two nematic phases

Proton-decoupled deuterium NMR spectra were obtained for an asymmetric liquid crystal dimer 1-(4-cyanobiphenyl-4′-yloxy)-6-(4-cyanobiphenyl-4′-yl)hexane (CB6OCB) containing a single -CD2- group. The sample has two nematic liquid crystal phases: a twist-bend nematic, NTB, at the lowest temperature followed by a uniaxial nematic, NU, on increasing the temperature. Proton decoupling reduces the linewidths of the peaks in the deuterium spectrum from kHz to ∼100Hz, enabling quadrupolar splittings, Δν, to be obtained with enhanced precision as well as the dipolar coupling between deuterium nuclei within the CD2 group, hence enhancing the information content.