A composition for preparing a poly(imide-amide) copolymer, comprising: a compound of Chemical Formula 10, a diamine represented by Chemical Formula 1, and the dianhydrides BPDA and 6FDA; wherein the compound of Chemical Formula 10 is a reaction product of TFDB with TPCl; and wherein an amount of the diamine represented by Chemical Formula 1 is 0.1 mol% to 10 mol% based on the total moles of TFDB and the diamine represented by Chemical Formula 1: wherein, in Chemical Formula 10, n0 is an integer of more than 0, (Chemical Formula 1) NH 2 -A-NH 2 wherein, in Chemical Formula 1, A is selected from chemical formulae of Group 1: wherein, in the chemical formulae, L is a single bond or a linking group selected from -O-, -S-, -C(=O)-, - CH -, -S(=O) 2 -, -Si(CH 3) 2 -, -(CH 2) p - (wherein, 1≤p≤10), -(CF 2) q - (wherein, 1≤q≤10), -CRR'- (wherein, R and R' are the same or different, and are independently hydrogen, a C1 to C4 alkyl group, a phenyl group, a phenyl group substituted with a C1 to C4 alkyl group, a C1 to C4 alkyl group substituted with a phenyl group, or a C1 to C4 alkyl group substituted with at least one fluorine atom, provided that R and R' are not simultaneously hydrogen), -C(=O)NH- and a fluorenylene group, and * indicates a point of attachment to a nitrogen atom, and * indicates a point of attachment to a nitrogen atom. a compound of Chemical Formula 10, a diamine represented by Chemical Formula 1, and the dianhydrides BPDA and 6FDA; wherein the compound of Chemical Formula 10 is a reaction product of TFDB with TPCl; and wherein an amount of the diamine represented by Chemical Formula 1 is 0.1 mol% to 10 mol% based on the total moles of TFDB and the diamine represented by Chemical Formula 1: wherein, in Chemical Formula 10, n0 is an integer of more than 0, (Chemical Formula 1) NH 2 -A-NH 2 wherein, in Chemical Formula 1, A is selected from chemical formulae of Group 1: wherein, in the chemical formulae, L is a single bond or a linking group selected from -O-, -S-, -C(=O)-, - CH -, -S(=O) 2 -, -Si(CH 3) 2 -, -(CH 2) p - (wherein, 1≤p≤10), -(CF 2) q - (wherein, 1≤q≤10), -CRR'- (wherein, R and R' are the same or different, and are independently hydrogen, a C1 to C4 alkyl group, a phenyl group, a phenyl group substituted with a C1 to C4 alkyl group, a C1 to C4 alkyl group substituted with a phenyl group, or a C1 to C4 alkyl group substituted with at least one fluorine atom, provided that R and R' are not simultaneously hydrogen), -C(=O)NH- and a fluorenylene group, and * indicates a point of attachment to a nitrogen atom, and * indicates a point of attachment to a nitrogen atom. L is a single bond or a linking group selected from -O-, -S-, -C(=O)-, - CH -, -S(=O) 2 -, -Si(CH 3) 2 -, -(CH 2) p - (wherein, 1≤p≤10), -(CF 2) q - (wherein, 1≤q≤10), -CRR'- (wherein, R and R' are the same or different, and are independently hydrogen, a C1 to C4 alkyl group, a phenyl group, a phenyl group substituted with a C1 to C4 alkyl group, a C1 to C4 alkyl group substituted with a phenyl group, or a C1 to C4 alkyl group substituted with at least one fluorine atom, provided that R and R' are not simultaneously hydrogen), -C(=O)NH- and a fluorenylene group, and * indicates a point of attachment to a nitrogen atom, and * indicates a point of attachment to a nitrogen atom.