AbstractSolid‐state polymerization of a binary mixture of nonliquid‐crystalline monomer and liquidcrystalline compound was carried out using electron beam. The monomers were benzoic acid containing 4‐[ω‐(meth)acryloyloxyalkyloxy] benzoic acids, in which the alkylene spacer was ethylene, hexamethylene, or undecamethylene. The conversion yield of monomer to polymer to a large extent increased with increasing content of a liquid‐crystalline compound with a terminal carboxylic group, such as 4‐n‐alkyloxybenzoic acid, while the addition of a liquid‐crystalline compound without terminal carboxylic group did not affect polymerization of the monomer. Phase diagrams of the mixture of monomer and liquid‐crystalline compound were examined using cross‐polarizing microscopy and differential scanning calorimetry (DSC). All mixtures of monomer and 4‐n‐alkyloxybenzoic acid or liquid‐crystalline compound without terminal carboxylic group showed liquid‐crystallinity in a broad composition range. It was concluded that liquid‐crystalline compounds with terminal carboxylic acid may form hydrogen bondings with methacrylate or acrylate monomer having terminal carboxylic acid which enhance polymerizability of the mixture. The stereoregularity of polymers determined by NMR depended on increasing irradiation dose and temperature rather than the content of the added liquid‐crys