The reaction product of formula or with the sulfide containing compound (C 3) G-(Z 1) r X 3 -S-S-X 4 -(Z 2) q -G, wherein X 1 is the direct bond; an optionally substituted, saturated or unsaturated, fused or non-fused aromatic or nonaromatic bivalent radical optionally comprising at least one heteroatom; a saturated or unsaturated, fused or non-fused aromatic or nonaromatic bivalent radical comprising at least one heteroatom, which is optionally substituted by C 1 -C 30 alkyl, C 1 -C 30 alkoxy, C 2 -C 12 alkenyl, C 5 -C 10 aryl, C 5 -C 10 cycloalkyl, C 1 -C 10 alkyl(C 5 -C 10 arylene), hydroxy or halogen; Y 1 is a residue of a cationically charged organic dye selected from azo, disazo, azomethine, hydrazomethine, merocyanine, methine, oxazine and styryl dyes; m, n and p are a number from 0 to 50000; wherein the sum of m and n ≥ 3; Z 1 and Z 2 independently from each other are -C -: -C 2 -C 12 alkenylene-; -(CH 2 CH 2 -O) 1-5 -; -C 1 -C 10 alkylene(C 5 -C 10 arylene)-; -C 5 -C 10 arylene-; -C 5 -C 10 cyclo-alkylene-; -C O-; -OCO-; -N(R 3)-;; -CON(R 4)-; -(R 5)NC -;-CH 2 C N(R 6)-, -(R 6)NC CH 2 -; -O-; -S-; -S -; or -S 2 -; X 3 and X 4 each independently from each other are unsubstituted or substituted, straight-chain or branched, interrupted or uninterrupted -C 1 -C 10 alkylene-; -C 5 -C 10 cycloalkylene-; C 5 -C 10 arylene, or -C 5 -C 10 arylene-(C 1 -C 10 alkylene)-; G represents a functional group capable of reacting with the polymeric backbone selected from halide, activated methoxy, hydroxy, tosylate, mesylate, carboxylic acid, carboxylic acid chloride, carboxylic ester, sulfonyl chloride, vinyl sulfone, acrylate, isocyanate, epoxide, anhydride, primary, secondary or tertiary amines and hydroxy; q and r, independently from each other, are 0 or 1; R 3, R 4, R 5 and R 6 independently from each other are hydrogen; unsubstituted or substituted, straight-chain or branched, monocyclic or polycyclic, interrupted or uninterrupted C 1 -C 14 alkyl; C 2 -C 14 alkenyl; C 6 -C 10 aryl; C 6 -C 10 aryl-C 1 -C 10 alkyl, or C 5 -C 10 alkyl(C 5 -C 10 aryl). X 1 is the direct bond; an optionally substituted, saturated or unsaturated, fused or non-fused aromatic or nonaromatic bivalent radical optionally comprising at least one heteroatom; a saturated or unsaturated, fused or non-fused aromatic or nonaromatic bivalent radical comprising at least one heteroatom, which is optionally substituted by C 1 -C 30 alkyl, C 1 -C 30 alkoxy, C 2 -C 12 alkenyl, C 5 -C 10 aryl, C 5 -C 10 cycloalkyl, C 1 -C 10 alkyl(C 5 -C 10 arylene), hydroxy or halogen; Y 1 is a residue of a cationically charged organic dye selected from azo, disazo, azomethine, hydrazomethine, merocyanine, methine, oxazine and styryl dyes; m, n and p are a number from 0 to 50000; wherein the sum of m and n ≥ 3; Z 1 and Z 2 independently from each other are -C -: -C 2 -C 12 alkenylene-; -(CH 2 CH 2 -O) 1-5 -; -C 1 -C 10 alkylene(C 5 -C 10 arylene)-; -C 5 -C 10 arylene-; -C 5 -C 10 cyclo-alkylene-; -C O-; -OCO-; -N(R 3)-;; -CON(R 4)-; -(R 5)NC -;-CH 2 C N(R 6)-, -(R 6)NC CH 2 -; -O-; -S-; -S -; or -S 2 -; X 3 and X 4 each independently from each other are unsubstituted or substituted, straight-chain or branched, interrupted or uninterrupted -C 1 -C 10 alkylene-; -C 5 -C 10 cycloalkylene-; C 5 -C 10 arylene, or -C 5 -C 10 arylene-(C 1 -C 10 alkylene)-; G represents a functional group capable of reacting with the polymeric backbone selected from halide, activated methoxy, hydroxy, tosylate, mesylate, carboxylic acid, carboxylic acid chloride, carboxylic ester, sulfonyl chloride, vinyl sulfone, acrylate, isocyanate, epoxide, anhydride, primary, secondary or tertiary amines and hydroxy; q and r, independently from each other, are 0 or 1; R 3, R 4, R 5 and R 6 independently from each other are hydrogen; unsubstituted or substituted, straight-chain or branched, monocyclic or polycyclic, interrupted or uninterrupted C 1 -C 14 alkyl; C 2 -C 14 alkenyl; C 6 -C 10 aryl; C 6 -C 10 aryl-C 1 -C 10 alkyl, or C 5 -C 10 alkyl(C 5 -C 10 aryl).