Structure and Molecular Ordering of a Nematic Liquid Crystal Studied by Natural-Abundance Double-Quantum ¹³C NMR

Abstract

We have studied the mesogenic molecule 4-n-pentyl-4‘-cyanobiphenyl (5CB) in the nematic phase by double-quantum 13C nuclear magnetic resonance (NMR). The experiment detects selectively the very rare isotopomers containing natural pairs of 13C spins. The 13C−13C dipolar couplings were interpreted in terms of the structure and orientational order of the cyanobiphenyl fragment. Different strategies were employed to analyze the internal motion of the core moiety. This is the first investigation of molecular conformation and order which exploits magnetic 13C−13C dipolar couplings in a non-labeled liquid crystal.