Crosslinked cyclohexane derivatives, and liquid-crystalline medium

A cyclohexane compound of formula I

• wherein
• B and B1, are each independently,
• where the rings B and B1 are each bonded to the group (X)p via the axial bond, and one or two non-adjacent CH2 groups in these rings are optionally replaced by O,
• Y is each independently C or Si,
• Q and Q1 are each independently CH or SiH,
• X is each independently —C≡C—, —CH═CH—, —CF═CF—, —CF═CH—, —CH2—, —COO— or 1,4-phenylene in which one or more CH groups are independently optionally replaced by N or CF,
• p is 1, 2, 3 or 4,
• R, R1, R2, R3 and R4 are each independently an alkyl radical having 1-12 carbon atoms which is unsubstituted or at least monosubstituted by halogen and in which one or more CH2 groups are independently optionally replaced by —O—, —S—, —CO—,
• —CO—O—, —O—CO—, —O—CO—O— or —CH═CH— in such a way that heteroatoms are not connected directly, or are CN, F, —CF3, —OCHF2, —OCF3, —OCHFCF3, —OCH2CF3, —OCF2—CF3 or —CH═CF2;
• and R4 can be H;
• A, A1, A2 and A3 are each independently
• or 1,4-phenylene in which one or more CH groups are replaced by N, where the rings A, A1, A2 and A3, are independently optionally substituted by at least one F atom, —NCS, —CN, —CF3 or —OCF3,
• Z, Z1, Z2 and Z3 are each independently —CO—O—, —O—CO—, —CH2O—, —CH═CH—, —O—, —O—CH2—, —CH2CH2—, —(CH2)3—, —(CH2)4—, —CF2—CF2—, —OCF2— or a single bond,
• and
• n, m, r and s are each independently 0, 1 or 2.