Liquid crystal aligning agent, liquid crystal alignment film, and display substrate

A liquid crystal aligning agent, comprising:

• at least one polymer selected from at least one of a polyamic acid and a group of polyimides obtained by ring closure of the polyamic acid, wherein
• the polyamic acid includes a first segment structure formed by a first dianhydride represented by a following formula (I) and a first diamine represented by a following formula (II), a second segment structure formed by a second dianhydride represented by a following formula (IV) and the first diamine, a third segment structure formed by a second diamine represented by a following formula (V) and the first dianhydride, and a fourth segment structure formed by the second diamine represented by the following formula (V) and the second dianhydride;
• wherein
• X1 in the first dianhydride is a first soft segment, Y2 in the second diamine is a second soft segment, and at least one of the first soft segment and the second soft segment is an amorphous segment;
• the first soft segment is a substituted or unsubstituted alkylene segment having 10 to 20 carbon atoms, the second soft segment is a substituted or unsubstituted alkylene segment having 5 to 12 carbon atoms, and the second soft segment is selected from a hydrophobic segment or a segment including at least one hydrophobic group;
• and L in the first dianhydride is selected from a single bond, a double bond or a divalent or trivalent hydrocarbon group having 1 to 3 carbon atoms;
• X2 in the second dianhydride is selected from a substituted or unsubstituted aliphatic ring, a substituted or unsubstituted aromatic ring, a substituted or unsubstituted heterocyclic ring, or a substituted or unsubstituted fused ring;
• in the first diamine represented by formula (II), Y1 is selected from a substituted aromatic ring, a substituted heterocyclic ring or a substituted fused ring, in each of which at least one carbon atom is substituted;
• and at least one substituent group is selected from a hydrophilic group or a hydrocarbon group having 1 to 3 carbon atoms and having at least one hydrophilic group;
• each of a single A1 and a single A2 is C, and the single A1 and the single A2 are both combined with Y1;
• remaining Als and remaining A2s are each independently selected from CH, CR or N, and neither of a number of Ns in the remaining A1s and a number of Ns in the remaining A2s is more than two;
• in the second diamine, each of a single A5 and a single A6 is C, and the single A5 and the single A6 are both combined with Y2;
• remaining A5s and remaining A6s are each independently selected from CH, CR or N, and neither of a number of Ns in the remaining A5s and a number of Ns in the remaining A6s is more than two;
• and
• R1, R2 and R are each independently selected from hydrogen or an aliphatic hydrocarbon group.