The present invention relates to method for treating a substrate or a surface thereof bearing Si—H groups to confer to it a physical and/or biochemical surface-modified property, wherein it comprises at least a step consisting of exposing, within a liquid medium, said substrate or a surface thereof with at least a polymer, said polymer containing: at least three reactive sites able to attach to said substrate or said surface by reacting with Si—H groups and further creating covalent bonds, and at least a molecule or a part thereof able to confer said modified property to said substrate or said surface thereof, said step being carried out in efficient conditions to promote the covalent grafting of said polymer to said substrate or surface thereof and the molecular weight of said polymer being greater than 1000 g/mol.