Polyamide-imide block copolymers, preparation method thereof and polyamide-imide film comprising the same

A polyamide-imide block copolymer comprising:

• a first repeat unit represented by the following Chemical Formula 1, a second repeat unit represented by the following Chemical Formula 2 and a third repeat unit represented by the following Chemical Formula 3:
• wherein, in the Chemical Formulae 1 to 3,
• each A is the same as or different from each other in each repeat unit, and is a substituted or unsubstituted tetravalent organic group,
• E1, E2, E3, E4, E5, E6 and E7 are the same as or different from each other in each repeat unit, and are a single bond or —NH—,
• each Z1 is the same as or different from each other in each repeat unit, and is a trivalent organic group derived from at least one compound selected from the group consisting of triacyl halide, triamine and tricarboxylic acid,
• each Z2 is the same as or different from each other in each repeat unit, and is a divalent organic group derived from at least one compound selected from the group consisting of diacyl halide, diamine and dicarboxylic acid, and
• Y1, Y2, and Y3 are the same as or different from each other in each repeat unit, and each independently, a divalent aromatic organic group having 6 to 30 carbon atoms, wherein the divalent aromatic organic group exists alone;
• or two or more aromatic organic groups are bonded to each other to form a divalent condensed ring;
• or two or more aromatic organic groups are linked by a single bond, a fluorenylene group, —O—, —S—, —C(═O)—, —CH(OH)—, —S(═O)2—, —Si(CH3)2—, —(CH2)p, where 1≤p≤10, —(CF2)q, where 1≤q≤10, —C(CH3)2—, —C(CF3)2—, or —C(═O)NH—, with the proviso that at least one of Y1, Y2 and Y3 is substituted with one or more photocurable functional groups selected from the group consisting of a (meth)acrylate group and a functional group represented by the following Chemical Formula 4,
• each R1 is the same as or different from each other in each repeat unit, and is hydrogen or an alkyl group having 1 to 10 carbon atoms, and each L is the same as or different from each other in each repeat unit, and is a single bond or an alkylene having 1 to 10 carbon atoms,
• wherein the sum of the repeat units in which Y1, Y2 and Y3 are substituted with the photocurable functional group is 20 mol % to 50 mol % based on 100 moles of the total repeat units, and
• wherein a weight average molecular weight is 5,000 to 300,000 g/mol.