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

1. 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,

R 2 is a substituted or unsubstituted phenylene group,

R 6 and R 7 are the same or different and are each independently an electron withdrawing group;

R 8 and R 9 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 —OR 204 , wherein R 204 is a C1 to C10 aliphatic organic group, or a silyl group of formula —SiR 205 R 206 R 207 wherein R 205 , R 206 , and R 207 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,

R 5 is a substituted or unsubstituted biphenylene group,

R 6 to R 9 , n3 and n4 are the same as defined in Chemical Formula 1;

wherein, in Chemical Formula 3,

R 10 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,

R 12 and R 13 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 —OR 208 , wherein R 208 is a C1 to C10 aliphatic organic group, or a silyl group of formula —SiR 209 R 210 R 211 , wherein R 209 , R 210 , and R 211 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

R 11 is represented by Chemical Formula 4:

wherein, in Chemical Formula 4,

R 6 to R 9 , 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.

2. The film according to claim 1 , wherein the structural unit represented by Chemical Formula 3 is represented by at least one of a structural unit represented by Chemical Formula 5 and a structural unit represented by Chemical Formula 6:

wherein, in Chemical Formulae 5 and 6,

R 11 to R 13 , n7, and n8 are the same as defined in Chemical Formula 3.

3. The film according to claim 2 , wherein the structural unit represented by Chemical Formula 5 and the structural unit represented by Chemical Formula 6 are present in the poly(imide-amide) copolymer in a mole ratio of about 1:99 to about 99:1.

4. The film according to claim 1 , wherein the electron withdrawing group is selected from —CF 3 , —CCl 3 , —CBr 3 , —Cl 3 , —NO 2 , —CN, —C(═O)CH 3 , and —CO 2 C 2 H 5 .

5. The film according to claim 1 , wherein the structural unit represented by Chemical Formula 1 is represented by at least one of a structural unit represented by Chemical Formula 7 and a structural unit represented by Chemical Formula 8:

6. The film according to claim 1 , wherein the structural unit represented by Chemical Formula 2 is represented by a structural unit represented by Chemical Formula 9:

7. The film according to claim 1 , wherein the structural unit represented by Chemical Formula 3 is represented by at least one of a structural unit represented by Chemical Formula 10 and a structural unit represented by Chemical Formula 11:

8. The film according to claim 1 , wherein the structural unit represented by Chemical Formula 1 is represented by Chemical Formula 7, the structural unit represented by Chemical Formula 2 is represented by the structural unit represented by Chemical Formula 9, and the structural unit represented by Chemical Formula 3 is represented by a combination of the structural unit represented by Chemical Formula 10 and the structural unit represented by Chemical Formula 11.

9. A display device comprising the film according to claim 1 .

10. The display device according to claim 9 , wherein the display device is a flexible display device.