Electrooptical liquid crystal system

A reactive liquid crystal compound of formula II

• R′—G′—R″ II
• wherein
• at least one of terminal groups R′ and R″ is a reactive group exhibiting one reaction site selected from HOW′2C—, HSW′2C—, UW′N—, a carboxyl group,
• and O═C—N—, or
• is a polymerizable reactive group exhibiting two or more reactive sites selected from
• W′2C═CW′—, and
• wherein W′ is in each case independently, H or an alkyl group with 1-5 C atoms, and
• one of terminal groups R′ and R″ is optionally an alkyl group of tip 15 C atoms which is unsubstituted or substituted by one or more halogens and in which one or more CH2 groups is in each case independently replaced by —O—, —S—, —CO—, —OCO—, —CO—O—, or —O—CO—O— wherein O atoms are not directly linked to one another,
• G′ is a rod-like diyl group of the formula
• —S1—(A5—Z3)m—A6—S2—
• wherein
• S1 and S2 are each alkylene groups with 0-20 C atoms which can be linear or branched, it also being possible for one or more CH2 groups to be replaced, in each case independently from each other, by —O—, —CO—, —S— or —NW′— with the proviso that O atoms are not linked directly to one another,
• A5 and A6 are, independently from each other,
• a) a cyclohexylene group, wherein one or two non-adjacent CH2 groups may be replaced by O or S atoms,
• b) an unsubstituted 1,4-phenylene group wherein one to three CH groups may be replaced by —N— or a 1,4-phenylene group which is mono- or polysubstituted by F, Cl and/or CH3,
• c) a bicyclo(2,2,2)octylene group, a naphthalene-2,6-diyl group, a decahydronaphthalene-2,6-diyl group or 1,2,3,4-tetrahydro-naphthalene group,
• Z3 is, independently from each other, —CO—O—, —O—CO—, —CH2CH2—, —CH2O—, —OCH2—, —C≡C— or a single bond, and
• m is 1, 2, 3, or 4;
• wherein
• at least one of group Z3 is C≡C—.