Compound having poly (difluoromethylene) chain, liquid crystal composition and liquid crystal display device

A liquid crystal composition, containing at least one compound represented by formula (1) as a first additive, wherein formula (1) is:

• Wherein in formula (1):
• R1 is alkyl having 3 to 15 carbons, alkyl having 2 to 15 carbons in which at least one of —CH2— is replaced by —O— or alkenyl having 4 to 15 carbons, and in the groups, at least one of hydrogen may be replaced by fluorine or chlorine;
• a is an integer from 2 to 12;
• and
• R2 is a group represented by formula (1a), formula (1b) or formula (1c):
• wherein, in formula (1a), formula (1b) and formula (1c),
• S1 and S2 are independently a single bond or alkylene having 1 to 10 carbons, and in the alkylene, at least one of —CH2— may be replaced by —O—, —NH—, —CO—, —COO—, —OCO— or —OCOO—, and at least one of —(CH2)2— may be replaced by —CH═CH—, and in the groups, at least one of hydrogen may be replaced by fluorine or chlorine;
• S3 is >CH— or >N—;
• S4 is >C< or >Si<;
• X1 is —OH, —NH2 or a group represented by —OR3, —N(R3)2 or —Si(R3)3, in which R3 is hydrogen or alkyl having 1 to 10 carbons, and in the alkyl, at least one of —CH2— may be replaced by —O—, at least one of —(CH2)2— may be replaced by —CH═CH—, and in the groups, at least one of hydrogen may be replaced by fluorine or chlorine;
• in which, in formula (1), a sum of carbons in R′, S1, S2, S3, S4 and —(CF2)a— is at least 11;
• and
• in which, a is 2, 3, 5, 7, 9, 10, 11 or 12 when R2 is a group represented by formula (1a), S1 is —(CH2)2— and X1 is —OH;
• and a is 2, 3, 4, 5, 6, 7, 9, 10, 11 or 12 when R2 is a group represented by formula (1a), S1 is —(CH2)3— and X1 is —OH.