A polymer of formula I wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings U S, Se or NR 0, X F, Cl or CN, R 1, R 2 H, F, R x, -OR x, -SR x, -C(=O)R x or -C(=O)-OR x, -S(=O)2R x, R 3, R 4 H, F, Cl, CN, R x, -OR x, -SR X, -C(=O)R x, -C(=O)-OR x or-S(=O) 2 R x, R 5 straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more CH 2 groups are optionally replaced by-O-, -S-, -C(=O)-, -C(=S)-, -C(=O)-O-, -O-C(=O)-, -NR 0 -,-SiR 0 R 00 -, -CF 2 -, -CR 0 =CR 00 -, -CY 1 =CY 2 - or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another, and in which one or more H atoms are optionally replaced by F, Cl, Br, I or CN, R x straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more CH 2 groups are optionally replaced by-O-, -S-, -C(=O)-, -C(=S)-, -C(=O)-O-, -O-C(=O)-, -NR 0 -,-SiR 0 R 00 -, -CF 2 -, -CR 0 =CR 00 -, -CY 1 =CY 2 - or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another, and in which one or more H atoms are optionally replaced by F or CN, or aryl, heteroaryl, arylalkyl or heteroarylalkyl, wherein each of the aforementioned cyclic groups has 5 to 20 ring atoms, is mono- or polycyclic, does optionally contain fused rings, and is unsubstituted or substituted by one or more identical or different groups L, L F, Cl, -NO 2, -CN, -NC, -NCO, -NCS, -OCN, -SCN, R 0, OR 0, SR 0, -C(=O)X 0, -C(=O)R 0, -C(=O)-OR 0, -O-C(=O)-R 0, -NH 2,-NHR 0, -NR 0 R 00, -C(=O)NHR 0, -C(=O)NR 0 R 00, -SO 3 R 0,-SO 2 R 0, -OH, -NO 2, -CF 3, -SF 5, or optionally substituted silyl, or carbyl or hydrocarbyl with 1 to 40 atoms that is optionally substituted and optionally comprises one or more hetero atoms, Y 1, Y 2 H, F, Cl or CN, R 0, R 00 H or straight-chain or branched alkyl with 1 to 30 C atoms that is optionally fluorinated, X 0 halogen, x, y real numbers representing mole fractions, wherein 0<x<1 and 0<y<1 and x+y=1, n an integer >1. U S, Se or NR 0, X F, Cl or CN, R 1, R 2 H, F, R x, -OR x, -SR x, -C(=O)R x or -C(=O)-OR x, -S(=O)2R x, R 3, R 4 H, F, Cl, CN, R x, -OR x, -SR X, -C(=O)R x, -C(=O)-OR x or-S(=O) 2 R x, R 5 straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more CH 2 groups are optionally replaced by-O-, -S-, -C(=O)-, -C(=S)-, -C(=O)-O-, -O-C(=O)-, -NR 0 -,-SiR 0 R 00 -, -CF 2 -, -CR 0 =CR 00 -, -CY 1 =CY 2 - or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another, and in which one or more H atoms are optionally replaced by F, Cl, Br, I or CN, R x straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more CH 2 groups are optionally replaced by-O-, -S-, -C(=O)-, -C(=S)-, -C(=O)-O-, -O-C(=O)-, -NR 0 -,-SiR 0 R 00 -, -CF 2 -, -CR 0 =CR 00 -, -CY 1 =CY 2 - or -C≡C- in such a manner that O and/or S atoms are not linked directly to one another, and in which one or more H atoms are optionally replaced by F or CN, or aryl, heteroaryl, arylalkyl or heteroarylalkyl, wherein each of the aforementioned cyclic groups has 5 to 20 ring atoms, is mono- or polycyclic, does optionally contain fused rings, and is unsubstituted or substituted by one or more identical or different groups L, L F, Cl, -NO 2, -CN, -NC, -NCO, -NCS, -OCN, -SCN, R 0, OR 0, SR 0, -C(=O)X 0, -C(=O)R 0, -C(=O)-OR 0, -O-C(=O)-R 0, -NH 2,-NHR 0, -NR 0 R 00, -C(=O)NHR 0, -C(=O)NR 0 R 00, -SO 3 R 0,-SO 2 R 0, -OH, -NO 2, -CF 3, -SF 5, or optionally substituted silyl, or carbyl or hydrocarbyl with 1 to 40 atoms that is optionally substituted and optionally comprises one or more hetero atoms, Y 1, Y 2 H, F, Cl or CN, R 0, R 00 H or straight-chain or branched alkyl with 1 to 30 C atoms that is optionally fluorinated, X 0 halogen, x, y real numbers representing mole fractions, wherein 0<x<1 and 0<y<1 and x+y=1, n an integer >1.