(Co)polyglutamates and (co)polyaspartates were grafted onto microparticulate silica and flat Si-OH containing surfaces, by initiating the N-carboxyl anhydrides of the corresponding cr-amino acids with an immobilized primary amine. The copolymers were prepared by polymerization of mixtures of N-carboxy anhydrides. In the case of microparticulate silica, all the available monomer was converted into grafted polymer, whereas in the case of flat surfaces, non-grafted material was formed as well. The grafted products were identified with infra-red spectroscopy and X-ray photoelectron spectroscopy.