A polymer, comprising (repeating) unit(s) of the formula and optionally wherein A is a repeating unit of the formula wherein a is 1, 2, or 3, a' is 0, 1, 2, or 3; b is 0, 1, 2, or 3; b' is 0, 1, 2, or 3; c is 0, 1, 2, or 3; c' is 0, 1, 2, or 3; d is 0, 1, 2, or 3; d' is 0, 1, 2, or 3; with the proviso that b' is not 0, if a' is 0; R 1 and R 2 may be the same or different and are selected from hydrogen, a C 1 -C 100 alkyl group, -COOR 103, a C 1 -C 100 alkyl group which is substituted by one or more halogen atoms, hydroxyl groups, nitro groups, -CN, or C 6 -C 13 aryl groups and/or interrupted by -O-, -COO-, - OCO-, or -S-; a C 7 -C 100 arylalkyl group, a carbamoyl group,C 5 -C 12 cycloalkyl, which can be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 3 alkoxy, a C 6 -C 24 aryl group, in particular phenyl or 1- or 2-naphthyl which can be substituted one to three times with C 1 -C 8 alkyl, C 1 -C 8 thioalkoxy, and/or C 1 -C 3 alkoxy, or pentafluorophenyl, R 103 is C 1 -C 50 alkyl, especially C 4 -C 25 alkyl; Ar 1 and Ar 1' are independently of each other Ar 2, Ar 2', Ar 3, Ar 3', Ar 4 and Ar 4' have the meaning of Ar 1, or are independently of each other wherein one of X 3 and X 4 is N and the other is CR 99, R 99, R 104 and R 104' are independently of each other hydrogen, halogen, especially F, or a C 1 -C 25 alkyl group, especially a C 4 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl, or a C 1 -C 25 alkoxy group, R 105 and R 105' independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 7 -C 25 arylalkyl, or C 1 -C 18 alkoxy, R 107 is H; C 6 -C 18 aryl; C 6 -C 13 aryl which is substituted by C 1 -C 18 alkyl, or C 1 -C 18 alkoxy; C 1 -C 18 alkyl; or C 1 -C 18 alkyl which is interrupted by -O-; and -COM 1 - is a repeating unit of formula or R 9 is C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 1 -C 25 perfluoroalkyl, C 1 -C 25 alkoxy, or CN; -COM 2 - is a second repeating unit -COM 1 -, which is different from the first repeating unit - COM 1 -, a second repeating unit -A-, which is different from the first repeating unit -A-, or a repeating unit of formula wherein one of X 5 and X 6 is N and the other is CR114, R 110 is a C 1 -C 25 alkyl group, especially a C 4 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl, or a C 1 -C 25 alkoxy group R 111, R 111', R 112 and R 112' are independently of each other hydrogen, halogen, especially F, or a C 1 -C 25 alkyl group, especially a C 4 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 arylalkyl, or a C 1 -C 25 alkoxy group, R 113 is C 6 -C 18 aryl; C 6 -C 13 aryl which is substituted by C 1 -C 13 alkyl, or C 1 -C 18 alkoxy; C 1 -C 18 alkyl; or C 1 -C 13 alkyl which is interrupted by -O-; R 114, R 114', R 115 and R 115' are independently of each other H, or a C 1 -C 25 alkyl group, especially a C 6 -C 25 alkyl, which may optionally be interrupted by one or more oxygen atoms; R 3 and R 3' are independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 7 -C 25 arylalkyl, or C 1 -C25alkoxy; R 5 and R 5' are independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 3 alkoxy; C 7 -C 25 arylalkyl, CN, or C 1 -C 25 alkoxy; or R 5 and R 5' together form a ring, R 55 and R 55' are independently of each other H, F, C 1 -C 18 alkyl, C 1 -C 18 alkyl which is interrupted by O, C 1 -C 18 alkoxy, C 1 -C 13 alkoxy which is interrupted by O, C 1 -C 18 perfluoroalkyl, C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 3 alkoxy, C 2 -C 20 heteroaryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 3 alkoxy; R 7 and R 7' are C 1 -C 25 alkyl, R 8 and R 8' are independently of each other hydrogen, C 6 -C 18 aryl; C 6 -C 13 aryl which is substituted by C 1 -C 13 alkyl, or C 1 -C 13 alkoxy; C 1 -C 25 alkyl, especially C 4 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; or C 7 -C 25 arylalkyl, R 11 and R 11' are independently of each other C 1 -C 35 alkyl group, C 7 -C 25 arylalkyl, or a phenyl group, which optionally can be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy, with the proviso that the following polymer (M n = 22.7 K; polydispersity = 2.1) is excluded.