A poly(imide-amide) copolymer, which is a product of a reaction between a diamine comprising an amide structural unit-containing oligomer represented by Chemical Formula 1 and a dianhydride represented by Chemical Formula 3: wherein, in Chemical Formula 1, R 1 and R 2 are the same or different, and are each independently selected from a halogen, a hydroxyl group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C1 to C10 alkoxy group, n0 is equal to or greater than 1, n1 and n2 are the same or different, and are each independently an integer from 0 to 4, provided that n1 + n2 is an integer ranging from 0 to 4, and Ar 1 and Ar 2 are the same or different and are each independently represented by Chemical Formula 2: wherein, in Chemical Formula 2, R 6 and R 7 are the same or different and are each independently an electron withdrawing group selected from -CF 3, -CCl 3, -CBr 3, -Cl 3, -NO 2, -CN, -C(=O)CH 3, and -CO 2 C 2 H 5, R 8 and R 9 are the same or different and are each independently a halogen, a hydroxyl group, a substituted or unsubstituted C1 to C10 aliphatic group, a substituted or unsubstituted C6 to C20 aromatic 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 a hydrogen or a C1 to C10 aliphatic organic group, and n3 is an integer from 1 to 4, n5 is an integer from 0 to 3, provided that n3 + n5 is an integer ranging from 1 to 4, n4 is an integer from 1 to 4, n6 is an integer from 0 to 3, provided that n4 + n6 is an integer ranging from 1 to 4; wherein, in Chemical Formula 3, R 10 is a single bond, or a substituted or unsubstituted C1 to C30 aliphatic 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 hydroxyl group, a substituted or unsubstituted C1 to C10 aliphatic group, a substituted or unsubstituted C6 to C20 aromatic group, an alkoxy group of formula - OR 205, wherein R 205 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 a hydrogen or a C1 to C10 aliphatic organic group, and n7 and n8 are the same or different and are each independently an integer ranging from 0 to 3, wherein a content of the amide structural unit derived from the amide structural unit-containing oligomer is equal to or greater than 60 mole percent to 70 mole percent based on the total mole number of the amide structural unit derived from the oligomer and the imide structural unit derived from the Chemical Formula 3. R 1 and R 2 are the same or different, and are each independently selected from a halogen, a hydroxyl group, a substituted or unsubstituted C1 to C10 alkyl group, a substituted or unsubstituted C6 to C20 aryl group, or a substituted or unsubstituted C1 to C10 alkoxy group, n0 is equal to or greater than 1, n1 and n2 are the same or different, and are each independently an integer from 0 to 4, provided that n1 + n2 is an integer ranging from 0 to 4, and Ar 1 and Ar 2 are the same or different and are each independently represented by Chemical Formula 2: R 6 and R 7 are the same or different and are each independently an electron withdrawing group selected from -CF 3, -CCl 3, -CBr 3, -Cl 3, -NO 2, -CN, -C(=O)CH 3, and -CO 2 C 2 H 5, R 8 and R 9 are the same or different and are each independently a halogen, a hydroxyl group, a substituted or unsubstituted C1 to C10 aliphatic group, a substituted or unsubstituted C6 to C20 aromatic 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 a hydrogen or a C1 to C10 aliphatic organic group, and n3 is an integer from 1 to 4, n5 is an integer from 0 to 3, provided that n3 + n5 is an integer ranging from 1 to 4, n4 is an integer from 1 to 4, n6 is an integer from 0 to 3, provided that n4 + n6 is an integer ranging from 1 to 4; R 10 is a single bond, or a substituted or unsubstituted C1 to C30 aliphatic 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 hydroxyl group, a substituted or unsubstituted C1 to C10 aliphatic group, a substituted or unsubstituted C6 to C20 aromatic group, an alkoxy group of formula - OR 205, wherein R 205 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 a hydrogen or a C1 to C10 aliphatic organic group, and n7 and n8 are the same or different and are each independently an integer ranging from 0 to 3, wherein a content of the amide structural unit derived from the amide structural unit-containing oligomer is equal to or greater than 60 mole percent to 70 mole percent based on the total mole number of the amide structural unit derived from the oligomer and the imide structural unit derived from the Chemical Formula 3.