Functionalizing the surface of a substrate in an ionic liquid medium

The present invention relates to a useful method for functionalizing the surface of a substrate having at least one hydroxyl function, comprising contacting all or part (s) of said surface with an ionic liquid matrix containing at least one so-called reactive molecule , carrying at least one reactive function, under conditions conducive to the establishment of a covalent bond between said reactive function of the molecule and a hydroxyl functionality of said surface.