Method for grafting a properties-imparting compound onto a polymeric substrate containing carbon-hydrogen (C-H) bonds, said method comprising: a) providing a substrate; b) coating the substrate with a properties-imparting compound comprising a photoactive aryl-azide moiety of formula: with X 1, X 2, X 3 and X 4 independently representing a hydrogen or a fluorine atom, a C 1 -C 6 alkyl group, NO 2 or OH, and L representing NH, -C O-, -S-, -C NH-, -NHC -, -OC -, -NHC NH-, -NHC NH-, -C NRC -with R representing a C 1 -C 6 alkyl or triazolyl, preferably NH, -C O-, -S-, -C NH-, -NHC -, -OC -, - NHC NH-, or -NHC NH-, even more preferably -C NH-, -NHC -, -C O-, NH or -NHC NH-, so as to obtain a homogeneous dry layer of said properties-imparting compound coated on at least part of the substrate, and to bring said aryl-azide moiety of formula into covalent bonding proximity with the carbon-hydrogen bonds of the substrate, provided that when said properties-imparting compound is a polymer, it is a block- or gradient-copolymer with a block or a region rich in repeated units A, said repeated units A comprising the aryl-azide moiety of formula as defined above; c) irradiating the coated substrate with a reactive light source, preferably a UV or an IR source, for a time t 1 sufficient to form nitrenes that undergo insertion reactions into carbon-hydrogen bonds of the substrate, t 1 being equal to or less than 30 minutes, thereby yielding a grafted polymeric substrate; d) optionally washing the obtained grafted polymeric substrate; e) repeating steps b), c) and optionally d) at least once, preferably and at most 9 times, even more preferably 4 times; and f) optionally drying the grafted substrate obtained at the end of step e), said properties-imparting compound providing anti-fouling properties, antibacterial properties, or rendering the substrate radio-opaque or visible in medical imaging, such as MRI fluorescence imaging or visible by near infrared imaging, and said method for grafting a properties-imparting compound onto a polymeric substrate being carried out directly on the polymeric substrate without any prior treatment step. a) providing a substrate; b) coating the substrate with a properties-imparting compound comprising a photoactive aryl-azide moiety of formula: with X 1, X 2, X 3 and X 4 independently representing a hydrogen or a fluorine atom, a C 1 -C 6 alkyl group, NO 2 or OH, and L representing NH, -C O-, -S-, -C NH-, -NHC -, -OC -, -NHC NH-, -NHC NH-, -C NRC -with R representing a C 1 -C 6 alkyl or triazolyl, preferably NH, -C O-, -S-, -C NH-, -NHC -, -OC -, - NHC NH-, or -NHC NH-, even more preferably -C NH-, -NHC -, -C O-, NH or -NHC NH-, so as to obtain a homogeneous dry layer of said properties-imparting compound coated on at least part of the substrate, and to bring said aryl-azide moiety of formula into covalent bonding proximity with the carbon-hydrogen bonds of the substrate, provided that when said properties-imparting compound is a polymer, it is a block- or gradient-copolymer with a block or a region rich in repeated units A, said repeated units A comprising the aryl-azide moiety of formula as defined above; with X 1, X 2, X 3 and X 4 independently representing a hydrogen or a fluorine atom, a C 1 -C 6 alkyl group, NO 2 or OH, and L representing NH, -C O-, -S-, -C NH-, -NHC -, -OC -, -NHC NH-, -NHC NH-, -C NRC -with R representing a C 1 -C 6 alkyl or triazolyl, preferably NH, -C O-, -S-, -C NH-, -NHC -, -OC -, - NHC NH-, or -NHC NH-, even more preferably -C NH-, -NHC -, -C O-, NH or -NHC NH-, so as to obtain a homogeneous dry layer of said properties-imparting compound coated on at least part of the substrate, and to bring said aryl-azide moiety of formula into covalent bonding proximity with the carbon-hydrogen bonds of the substrate, provided that when said properties-imparting compound is a polymer, it is a block- or gradient-copolymer with a block or a region rich in repeated units A, said repeated units A comprising the aryl-azide moiety of formula as defined above; c) irradiating the coated substrate with a reactive light source, preferably a UV or an IR source, for a time t 1 sufficient to form nitrenes that undergo insertion reactions into carbon-hydrogen bonds of the substrate, t 1 being equal to or less than 30 minutes, thereby yielding a grafted polymeric substrate; d) optionally washing the obtained grafted polymeric substrate; e) repeating steps b), c) and optionally d) at least once, preferably and at most 9 times, even more preferably 4 times; and f) optionally drying the grafted substrate obtained at the end of step e), said properties-imparting compound providing anti-fouling properties, antibacterial properties, or rendering the substrate radio-opaque or visible in medical imaging, such as MRI fluorescence imaging or visible by near infrared imaging, and said method for grafting a properties-imparting compound onto a polymeric substrate being carried out directly on the polymeric substrate without any prior treatment step.