Bimesogenic compounds and flexoelectric devices

A bimesogenic compound of formula I

• R1-MG1-X1-Sp-X2-MG2-R2 I
• wherein
• R1 and R2 are each independently F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by —O—, —S—, —NH—, —N(CH3)—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another,
• MG1and MG2 are each independently a mesogenic group,
• Sp is a spacer group comprising 4 to 40 C atoms, wherein one or more non-adjacent CH2 groups may also be replaced by —O—, —S—, —NH—, —N(CH3)—, —CO—, —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O—, —CH(halogen)-, —CH(CN)—, —CH═CH— or —-C≡C—, and
• X1and X2 are each independently —O—, —S—, —CO—, —COO—, —OCO—, —O—CO—O—, —CO—NH—, —NH—CO—, —CH2CH2—, —OCH2—, —CH2O—, —SCH2—, —CH2S—, —CH═CH—, —CH═CH—COO—, —OCO—CH═CH—, —C≡C — or a single bond,
• wherein at least one of the mesogenic groups MG1 and MG2 comprises one or more linking groups selected from —CF2O— and —OCF2—.