Poly(imide-amide) copolymer, a method for preparing a poly(imide-amide) copolymer, and an article including a poly(imide-amide) copolymer

A film comprising a poly(imide-amide) copolymer, the poly(imide-amide) copolymer consisting of:

• a structural unit represented by Chemical Formula 1;
• a structural unit represented by Chemical Formula 2;
• and
• any one of a structural unit represented by Chemical Formula 3, a structural unit of an amic acid precursor of the structural unit represented by Chemical Formula 3, and a combination thereof;
• wherein the film has a tensile modulus of greater than or equal to about 5.5 gigapascals according to an ASTM D882 method, and a yellowness index of less than or equal to about 5 according to an ASTM D 1925 method, when the film has a thickness of about 50 micrometers:
• wherein, in Chemical Formula 1,
• R2 is a substituted or unsubstituted phenylene group,
• R6 and R7 are the same or different and are each independently an electron withdrawing group;
• R8 and R9 are the same or different, and are each independently a halogen, a hydroxy group, a substituted or unsubstituted C1 to C10 aliphatic organic group, a C6 to C20 aromatic organic group, an alkoxy group of formula —OR204, wherein R204 is a C1 to C10 aliphatic organic group, or a silyl group of formula —SiR205R206R207 wherein R205, R206, and R207 are the same or different, and are each independently hydrogen or a C1 to C10 aliphatic organic group,
• n3 is an integer ranging from 1 to 4, n5 is an integer ranging from 0 to 3, provided that n3+n5 is an integer ranging from 1 to 4, and
• n4 is an integer ranging from 1 to 4, n6 is an integer ranging from 0 to 3, provided that n4+n6 is an integer ranging from 1 to 4;
• wherein, in Chemical Formula 2,
• R5 is a substituted or unsubstituted biphenylene group,
• R6 to R9, n3 and n4 are the same as defined in Chemical Formula 1;
• wherein, in Chemical Formula 3,
• R10 is single bond, a substituted or unsubstituted C1 to C30 aliphatic organic group, a substituted or unsubstituted C3 to C30 alicyclic organic group, a substituted or unsubstituted C6 to C30 aromatic organic group, or a substituted or unsubstituted C2 to C30 heterocyclic group,
• R12 and R13 are the same or different, and are each independently a halogen, a hydroxy group, a substituted or unsubstituted C1 to C10 aliphatic organic group, a C6 to C20 aromatic organic group, an alkoxy group of formula —OR208, wherein R208 is a C1 to C10 aliphatic organic group, or a silyl group of formula —SiR209R210R211, wherein R209, R210, and R211 are the same or different, and are each independently hydrogen or a C1 to C10 aliphatic organic group,
• n7 and n8 are each independently an integer ranging from 0 to 3, and
• R11 is represented by Chemical Formula 4:
• wherein, in Chemical Formula 4,
• R6 to R9, n3 and n4 are the same as defined in Chemical Formula, and
• wherein a mole ratio of the sum of the structural unit represented by Chemical Formula 1 and the structural unit represented by Chemical Formula 2, and the structural unit represented by Chemical Formula 3 is about 20:80 to about 80:20.