Liquid-crystal compounds and LC media

A compound of formula I

• in which
• R1 denotes H, F, Cl, Br, —CN, —SCN, —NCS, SF5 or straight-chain or branched alkyl having 1 to 12 C atoms, in which, in addition, one or more non-adjacent CH2 groups may each be replaced, independently of one another, by —C≡C—, —CO—, —CO—O—, —O—CO—, —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl or Br, or P-Sp-,
• R2 denotes H or an unsubstituted alkyl having 1 to 5 C atoms,
• P denotes a polymerizable group,
• Sp denotes a spacer group or a single bond,
• A1 on each occurrence, identically or differently, denotes phenylene-1,4-diyl, in which, in addition, one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH3, CHF2, CH2F, OCH3, OCHF2 or OCF3,
• cyclohexane-1,4-diyl, in which, in addition, one or two non-adjacent CH2 groups may be replaced, independently of one another, by O and/or S, and one or more H atoms may be replaced by F,
• cyclohexene-1,4-diyl, bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, tetrahydropyran-2,5-diyl or 1,3-dioxane-2,5-diyl,
• Z1 and Z2 each, independently of one another, denote —CF2O—, —OCF2—, —CH2O—, —OCH2—, —C2H4—, —C2F4—, —CF2CH2—, —CH2CF2—, —CFHCFH—, —CFHCH2—, —CH2CFH—, —CF2CFH—, —CFHCF2—, —CH═CH—, —CF═CH—, —CH═CF—, —CF═CF—, —C≡C— or a single bond, and
• m denotes 0, 1, 2 or 3.