A polymer comprising at least one repeating unit, wherein the at least one repeating unit has Formula wherein each R1 and R2 is independently selected from a group consisting of H, R6, R21, SR6, SR21, SC R6, SC R21, OR6, OR21, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, NHC R6, NHC R21, NHC NHR6, NHC NHR21, N+ 3, N 3, NOz, NOR6, CN, and halogen; or R1 and R2, together with the carbon atoms to which they are attached to, form a saturated or partly unsaturated mono-, bi-, tri- or tetracyclic cycloalkyl or heterocycle optionally substituted with one or more SR21, SR6, SC R6, SC R21, OR21, OR6, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, N+ 3, R6, R21, halogen, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 2-10 -alkynyl, C 1-5 -haloalkyl; a mono-, bi-, tri-, tetra- or pentacyclic aryl or heteroaryl optionally substituted with one or more SR21, SR6, SC R6, SC R21, OR21, OR6, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, N+ 3, R6, R21, halogen, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 2-10 -alkynyl, C 1-5 -haloalkyl; R6 is each independently selected from a group consisting of H, C 1-20 -alkyl, C 2-20 -alkenyl, C 2-20 -alkynyl, C 1-10 -alkylenyl, C 1-10 -haloalkyl, and phenyl; R21 is each independently selected from C 1-10 -alkylenyl-CO 2 H, C 1-10 -alkylenyl-OH, C 1-10 -alkylenyl-NHR6, C 1-10 -alkylenyl-SH, C 1-10 -alkylenyl-N(O=CC=C)C=O, C 1-10 -alkylenyl-S-C 1-10 -alkylenyl-S-C 1-10 -alkylenyl-N(O=CC=C)C=O, (CH 2 CH 2 O) m CH 2 CH 2 -N(O=CC=C)C=O, C 1-10 -alkylenyl-S-S-C 1-10 -alkylenyl-CO 2 H, (CH 2 CH 2 O) m -C 1-10 -alkylenyl-S-S-C 1-10 -alkylenyl-CO 2 H, C 2-20 -alkynyl, (CH 2 CH 2 O) m H, (CH 2 CH 2 O) n CH 2 CH 2 SH, (CH 2 CH 2 O) n CH 2 CH 2 N 2, C 1-10 -alkylenyl, C 1-10 -haloalkyl, optionally substituted with one or more halogen, COzR6, OR6, N 2, N+ 3, SR6, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 1-10 -haloalkyl, C 1-10 -alkylenyl-COzH, C 1-10 -alkylenyl-OH, C 1-10 -alkylenyl-N 2, phenyl; m is an integer from 1 to 100; n is an integer from 1 to 100; or R1 and R2 together form a double bond between the carbon atoms they are attached to, and with the proviso that R1 and R2 are not all hydrogen at the same time, or a salt thereof. each R1 and R2 is independently selected from a group consisting of H, R6, R21, SR6, SR21, SC R6, SC R21, OR6, OR21, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, NHC R6, NHC R21, NHC NHR6, NHC NHR21, N+ 3, N 3, NOz, NOR6, CN, and halogen; or R1 and R2, together with the carbon atoms to which they are attached to, form a saturated or partly unsaturated mono-, bi-, tri- or tetracyclic cycloalkyl or heterocycle optionally substituted with one or more SR21, SR6, SC R6, SC R21, OR21, OR6, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, N+ 3, R6, R21, halogen, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 2-10 -alkynyl, C 1-5 -haloalkyl; a mono-, bi-, tri-, tetra- or pentacyclic aryl or heteroaryl optionally substituted with one or more SR21, SR6, SC R6, SC R21, OR21, OR6, OC R6, OC R21, OC NHR6, OC NHR21, NR6R21, N 2, N+ 3, R6, R21, halogen, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 2-10 -alkynyl, C 1-5 -haloalkyl; R6 is each independently selected from a group consisting of H, C 1-20 -alkyl, C 2-20 -alkenyl, C 2-20 -alkynyl, C 1-10 -alkylenyl, C 1-10 -haloalkyl, and phenyl; R21 is each independently selected from C 1-10 -alkylenyl-CO 2 H, C 1-10 -alkylenyl-OH, C 1-10 -alkylenyl-NHR6, C 1-10 -alkylenyl-SH, C 1-10 -alkylenyl-N(O=CC=C)C=O, C 1-10 -alkylenyl-S-C 1-10 -alkylenyl-S-C 1-10 -alkylenyl-N(O=CC=C)C=O, (CH 2 CH 2 O) m CH 2 CH 2 -N(O=CC=C)C=O, C 1-10 -alkylenyl-S-S-C 1-10 -alkylenyl-CO 2 H, (CH 2 CH 2 O) m -C 1-10 -alkylenyl-S-S-C 1-10 -alkylenyl-CO 2 H, C 2-20 -alkynyl, (CH 2 CH 2 O) m H, (CH 2 CH 2 O) n CH 2 CH 2 SH, (CH 2 CH 2 O) n CH 2 CH 2 N 2, C 1-10 -alkylenyl, C 1-10 -haloalkyl, optionally substituted with one or more halogen, COzR6, OR6, N 2, N+ 3, SR6, N 3, NOz, NOR6, CN, C 1-10 -alkyl, C 2-10 -alkenyl, C 1-10 -haloalkyl, C 1-10 -alkylenyl-COzH, C 1-10 -alkylenyl-OH, C 1-10 -alkylenyl-N 2, phenyl; m is an integer from 1 to 100; n is an integer from 1 to 100; or R1 and R2 together form a double bond between the carbon atoms they are attached to, and with the proviso that R1 and R2 are not all hydrogen at the same time, or a salt thereof.