Polymerizable compounds and their use in liquid crystal media and liquid crystal displays

A liquid crystal medium comprising one or more compounds of formula I

• Pa-(Spa)s1-(A1-Z1)n1-A2-Q1-A3-(Z4-A4)n2-(Spb)s2-Pb I
• in which the individual radicals have the following meanings:
• Pa, Pb each, independently of one another, denote a polymerizable group,
• Spa, Spb each, independently of one another, denote a spacer group,
• s1, s2 each, independently of one another, denote 0 or 1,
• n1 denotes 0 or 1,
• n2 denotes 0,
• Q1 denotes —CF2O—,
• Z1, Z4 each independently of one another, denote a single bond, —CF2O—, —OCF2—, —CH2O—, —OCH2—, —(CO)O—, —O(CO)—, —(CH2)4—, —CH2CH2—, —CF2—CF2—, —CF2—CH2—, —CH2—CF2—, —CH═CH—, —CF═CF—, —CF═CH—, —(CH2)3O—, —O(CH2)3—, —CH═CF—, —C≡C—, —O—, —CH2—, —(CH2)3—, or —CF2—,
• where Z1 and Q1 or Z4 and Q1 do not simultaneously denote —CF2O—,
• A2 denotes
• A3 denotes
• and
• A1, A4
• each, independently of one another, denotes a radical selected from the following groups:
• a) the group consisting of 1,4-phenylene and 1,3-phenylene, in which, in addition, one or two CH groups may each be replaced by N and in which, in addition, one or more H atoms may each be replaced by L,
• b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexylene and 1,4′-bicyclohexenylene, in which, in addition, one or more non-adjacent CH2 groups may each be replaced by —O— or —S— and in which, in addition, one or more H atoms may each be replaced by F or Cl,
• c) the group consisting of tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl, piperidine-1,4-diyl, thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may, in addition, be mono- or polysubstituted by L, and
• d) the group consisting of saturated, partially unsaturated or fully unsaturated, and optionally substituted, polycyclic radicals having 5 to 20 cyclic C atoms, one or more of which may also be replaced by heteroatoms,
• where, in addition, one or more H atoms in these radicals may each be replaced by L, and/or one or more double bonds may each be replaced by single bonds, and/or one or more CH groups may be replaced by N,
• L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF5 or straight-chain or branched, in each case optionally fluorinated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having up to 12 C atoms,
• or a polymer obtainable by polymerization of one or more compounds of the formula I.