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 -${\mathrm{CD}}_2$- group. The sample has two nematic liquid crystal phases: a twist-bend nematic, $N_{TB}$, at the lowest temperature followed by a uniaxial nematic, $N_U$, on increasing the temperature. Proton decoupling reduces the linewidths of the peaks in the deuterium spectrum from kHz to $\sim 100\mathrm{Hz}$, enabling quadrupolar splittings, $\mathrm{\Delta }\nu$, to be obtained with enhanced precision as well as the dipolar coupling between deuterium nuclei within the ${\mathrm{CD}}_2$ group, hence enhancing the information content.