A composition for preparing an article including a polyimide or poly(imide-amide) copolymer, the composition including (1) a solution including at least one of (i) a polymer including at least one selected from a structural unit represented by Chemical Formula 1 and a structural unit represented by Chemical Formula 2; and (ii) a copolymer including at least one selected from a structural unit represented by Chemical Formula 1 and a structural unit represented by Chemical Formula 2, and a structural unit represented by Chemical Formula 3, and (2) a metallic salt soluble in the solution of the polymer and/or the copolymer, wherein the metallic salt is a salt of a metal selected from a Group 1 element, a Group 11 element, a Group 13 element, and a Group 14 element: wherein in Chemical Formulae 1 to 3, A, B, D, and E are the same as defined in the detailed description.