A polymer represented by the following Chemical Formula 1: [Chemical Formula 1] E1- a - b - c -E2 wherein, in Chemical Formula 1, A1 is represented by the following Chemical Formula 2, B1 is represented by the following Chemical Formula 3, C1 is a substituted or unsubstituted arylene group; or a substituted or unsubstituted divalent heterocyclic group, and E1 and E2 are the same as or different from each other, and are each independently hydrogen; deuterium; a substituted or unsubstituted alkyl group; a substituted or unsubstituted silyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted arylamine group; a substituted or unsubstituted siloxane group; a crosslinkable group; or a combination thereof, a, b, and c are each a mole fraction, a is a real number of 0<a≤1, b is a real number of 0≤b<1, c is a real number of 0≤c<1, a + b + c = 1, in Chemical Formula 2, Ar1, Ar2, L1 and L2 are the same as or different from each other, and are each independently a substituted or unsubstituted arylene group, R1 to R3 are the same as or different from each other, and are each independently hydrogen; deuterium; a halogen group; a substituted or unsubstituted alkyl group; a substituted or unsubstituted silyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heterocyclic group; a substituted or unsubstituted arylamine group; or a substituted or unsubstituted siloxane group, R10 to R13 are the same as or different from each other, and are each independently a substituted or unsubstituted alkyl group, n1 to n3 are each an integer from 1 to 4, when n1 to n3 are each 2 or higher, the substituents in each parenthesis are the same as or different from each other, l1 and l2 are each an integer from 1 to 5, when l1 and l2 are each 2 or higher, the structures in each parenthesis are the same as or different from each other, * is an attachment point in the polymer, in Chemical Formula 3, m is an integer of 3 or 4, when m is 3, Z is CRa; SiRa; N; or a substituted or unsubstituted trivalent aryl group, when m is 4, Z is C; Si; or a substituted or unsubstituted tetravalent aryl group, Ra is hydrogen; deuterium; a substituted or unsubstituted alkyl group; or a substituted or unsubstituted aryl group, Y is a direct bond; a substituted or unsubstituted alkylene group; or a substituted or unsubstituted arylene group, when Y is a direct bond; or a substituted or unsubstituted alkylene group, Z is a substituted or unsubstituted trivalent or tetravalent aryl group, and * is an attachment point in the polymer. A1 is represented by the following Chemical Formula 2, B1 is represented by the following Chemical Formula 3, C1 is a substituted or unsubstituted arylene group; or a substituted or unsubstituted divalent heterocyclic group, and E1 and E2 are the same as or different from each other, and are each independently hydrogen; deuterium; a substituted or unsubstituted alkyl group; a substituted or unsubstituted silyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted arylamine group; a substituted or unsubstituted siloxane group; a crosslinkable group; or a combination thereof, a, b, and c are each a mole fraction, a is a real number of 0<a≤1, b is a real number of 0≤b<1, c is a real number of 0≤c<1, a + b + c = 1, in Chemical Formula 2, Ar1, Ar2, L1 and L2 are the same as or different from each other, and are each independently a substituted or unsubstituted arylene group, R1 to R3 are the same as or different from each other, and are each independently hydrogen; deuterium; a halogen group; a substituted or unsubstituted alkyl group; a substituted or unsubstituted silyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heterocyclic group; a substituted or unsubstituted arylamine group; or a substituted or unsubstituted siloxane group, R10 to R13 are the same as or different from each other, and are each independently a substituted or unsubstituted alkyl group, n1 to n3 are each an integer from 1 to 4, when n1 to n3 are each 2 or higher, the substituents in each parenthesis are the same as or different from each other, l1 and l2 are each an integer from 1 to 5, when l1 and l2 are each 2 or higher, the structures in each parenthesis are the same as or different from each other, * is an attachment point in the polymer, in Chemical Formula 3, m is an integer of 3 or 4, when m is 3, Z is CRa; SiRa; N; or a substituted or unsubstituted trivalent aryl group, when m is 4, Z is C; Si; or a substituted or unsubstituted tetravalent aryl group, Ra is hydrogen; deuterium; a substituted or unsubstituted alkyl group; or a substituted or unsubstituted aryl group, Y is a direct bond; a substituted or unsubstituted alkylene group; or a substituted or unsubstituted arylene group, when Y is a direct bond; or a substituted or unsubstituted alkylene group, Z is a substituted or unsubstituted trivalent or tetravalent aryl group, and * is an attachment point in the polymer.