¹³C magnetic resonance study of the isotropic and nematic phases of 4‐cyano‐benzylidene‐4^′‐octyloxyaniline

¹³C magnetic resonance is used to examine molecular ordering and dynamics in the nematogen 4‐cyano‐benzylidene‐4^′‐octyloxyaniline (CBOOA). A simple, self‐consistent model is proposed for evaluating the nematic phase uniaxial order parameter from the large downfield chemical shifts shown by the aromatic carbons on passing from the isotropic to the nematic phase. These results are an extension of the earlier observations of Pines and Chang on the related nematogen 4‐methoxy‐benzylidene‐4^′‐butylaniline (MBBA). A series of T₁ relaxation measurements are also reported and the relevant nuclear couplings for analyzing these results are identified. The results are interpreted in terms of (a) molecular scale reorientational diffusion with an axially symmetric orientational distribution function and (b) reorientation by collective angular modes.