mesogenic group
A part of a molecule or macromolecule endowed with sufficient anisotropy in both attractive and repulsive forces to contribute strongly to mesophase or, in particular, liquid-crystal mesophase formation in low-molar-mass and polymeric substances.
PAC, 2002, 74, 493. 'Definitions of basic terms relating to polymer liquid crystals (IUPAC Recommendations 2001)' on page 497 (