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-crystalmesophase formation in low-molar-mass and polymeric substances.
Source:
PAC, 2002, 74, 493 (Definitions of basic terms relating to polymer liquid crystals(IUPAC Recommendations 2001)) on page 497