Liquid crystal aligning agent, method of forming a liquid crystal alignment film and liquid crystal display element

A liquid crystal aligning agent comprising a polymer having a structure represented by the following formula (I):

• wherein S1 is a divalent organic group,
• T1 is a tetravalent organic group, and
• Z1 and Z2 are each independently a hydroxyl group or monovalent organic group, wherein at least one of Z1 and Z2 is at least one group selected from the group consisting of a monovalent organic group represented by formula (II):
• —R2—P2—CH═CH—CO—Q2 (II)
• wherein Q2 is a monovalent organic group having an aromatic ring,
• P2 is a divalent organic group having an aromatic ring, and
• R2 is a divalent bonding group,
• and a monovalent organic group represented by formula (III):
• —R3—P3—CO—CH═CH—Q3 (III)
• wherein Q3 is a monovalent organic group having an aromatic ring,
• P3 is a divalent organic group having an aromatic ring, and
• R3 is a divalent bonding group.