Liquid crystal compounds

A compound of formula (I)

• wherein
• G1 and G2 independently represent a polymerisable mesogenic substituent;
• Ar represents an aromatic group selected from the group consisting of phenyl or naphthalenediyl;
• w is 1 or 2;
• X represents a group selected from the group consisting of —CH2—, —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— and —OCONR′;
• Sp represents a group of the formula —(CH2)p- in which p is an integer of 1 to 18 and in which one or two non-adjacent —CH2— groups are optionally replaced by —CH═CH—;
• or in which one or two —CH2— groups are optionally replaced by one or two groups selected from the group consisting of —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO— and —OCONR′ with the proviso that firstly the spacer group does not contain two adjacent heteroatoms and secondly when X is —CH2—, p can also have a value of 0;
• and
• M represents an achiral group of formula (II)
• in which
• A and B independently represent an optionally substituted six membered isocyclic or heterocyclic group or naphthalenediyl;
• C is selected from the group consisting of an optionally substituted five and six membered isocyclic or heterocyclic group or naphthalenediyl;
• n1 and n2 are 0 or 1 with the proviso that firstly 1≤n1+n2≤2 and secondly, when C is naphthalenediyl 0≤n1+n2≤2;
• Z1 is selected from the group consisting
• of —O—, —COO—, —OOC—, —CO—, —CONR′—, —NR′CO—,
• OCOO—, —OCONR′—, —NR′COO— and a single bond;
• in which
• R′ is selected from the group consisting of hydrogen, a lower achiral alkyl group and a lower achiral alkenyl group;
• Z2 and Z3 are independently selected from the group consisting of single bond, —COO—, —OOC—, —CH2—CH2—, —CH2O—, —OCH2—, —CH═CH—, —C≡C—, —(CH2)4— and —(CH2)3O—;
• and
• R1 is selected from the group consisting
• of —CN, —COR, —COOR, —OCOR, —CONR′R, —NR′COR,
• OCOOR, —OCONR′R, —NR′COOR, —F, —Cl, —CF3, —OCF3, —OR and —R
• in which
• R is selected from the group consisting of hydrogen, an achiral C1-18 alkyl group and an achiral C4-18 alkenyl group with the double bond at 3-position or higher;
• and
• R′ is as defined above;
• wherein the polymerisable mesogenic substituents G1 and G2 are each independently represented by the group of formula III
• wherein
• D is selected from the group consisting of 1,4-naphthalenediyl, 2,6-naphthalenediyl and 1,5-naphthalenediyl
• E is selected from the group consisting of optionally substituted 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, trans- 1,4-cyclohexylene, trans- 1,4-cyclohexane,
• trans-1,3-dioxane-2,5-diyl, 1,4-naphthalenediyl, 2,6-naphthalenediyl and 1,5-naphthalenediyl;
• m is 1 or 0,
• Z4 and Z5 are independently selected from the group consisting of
• a single bond, —COO—, —OOC—,
• —OCOO—, —CH2—CH2—, —CH2O—, —OCH2—, —CH═CH—, —C≡C—, —(CH2)4— and —(CH2)3O—;
• Z6 represents a group of formula —(CH2)qX— in which q is an integer having a value of 1 to 18 and X is as defined above, and in which one or two non-adjacent —CH2— groups may be optionally replaced by —CH═CH— or in which one or two —CH2— groups may be replaced by one or two additional linking groups X with the proviso that firstly the group Z6 does not contain two adjacent heteroatoms and secondly when X is —CH2, q can also have a value of 0;
• and
• R2 represents a polymerisable group selected from the group consisting of CH2═C(Ph)-,
• CH2═CW—COO—, CH2═CH—COO-Ph-, CH2═CW—CO—NH—, CH2═CH—O—, CH2═CH—OOC—,
• Ph-CH═CH—, CH2═CH-Ph-, CH2═CH-Ph-O—, R3-Ph-CH═CH—COO—,
• R3—OOC—CH═CH-Ph-O— and 2-W-epoxyethyl,
• in which
• W represents H, Cl, Ph or a lower alkyl, and
• R3 represents a lower alkyl with the proviso that when R3 is attached to a phenylene group (-Ph-) it may also represent hydrogen or a lower alkoxy.