Polymerizable compound, polymerizable composition, polymer, and optically anisotropic product

A compound represented by a formula (IIa),

• wherein
• each of Y1 to Y8 independently represents a chemical single bond, —O—, —S—, —O—C(═O)—, —C(═O)—O—, —O—C(═O)—O—, —NR1—C(═O)—, —C(═O)—NR1—, —O—C(═O)—NR1—, —NR1—C(═O)—O—, —NR1—C(═O)—NR1—, —O—NR1—, or —NR1—O—,
• R1 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
• each of G1 and G2 independently represents a divalent linear aliphatic group having 1 to 20 carbon atoms that optionally includes —O—, —O—C(═O)—, —C(═O)—O—, or —C(═O)—,
• each of Z1 and Z2 independently represents an alkenyl group having 2 to 10 carbon atoms that is substituted with a halogen atom, or unsubstituted,
• Ax represents a group represented by a formula (II),
• wherein
• X represents —NR2—, an oxygen atom, a sulfur atom, and R2 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, provided that an arbitrary C—H is optionally substituted with a nitrogen atom,
• D represents an alkylene group having 1 to 20 carbon atoms that optionally includes —O—, —S—, —O—C(═O)—, —C(═O)—O—, —O—C(═O)—O—, —NR3—C(═O)—, —C(═O)—NR3—, —NR3—, or —C(═O)—, or a cycloalkanediyl group having 3 to 20 carbon atoms, provided that a case where the alkylene group includes two or more contiguous —O— or —S— is excluded, and R3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
• A1 represents a trivalent aromatic group,
• each of A1 and A3 independently represents a divalent alicyclic hydrocarbon group having 3 to 30 carbon atoms,
• each of A4 and A5 independently represents a divalent aromatic group having 4 to 30 carbon atoms,
• Q1 represents a hydrogen atom, or an alkyl group having 1 to 6 carbon atoms, and m and n are independently 0 or 1.