The invention relates to novel materials based on biodegradable polyamino acids that are useful for vectorizing active principle(s)(AP). The aim of the invention is to supply a new polymeric raw material that is used for vectorizing AP and optimally fulfills all requirements concerning biocompatibility, biodegradability, the ability to be easily associated with numerous active principles or solubilize the active principles and to release the active principles in vivo. Such polymers can also be readily and economically transformed into particles vectorizing active principles according to the grafting rate of the hydrophobic groups, said particles being able to form stable aqueous colloidal suspensions. The aim of the invention is achieved by the inventive amphiphile polyamino acids comprising aspartic and/or glutamic units that carry grafts which encompass at least one hydrophobic unit and are linked to the aspartic and/or glutamic units via a rotula containing two amide functions, more particularly via a spacer of the lysine or ornithine type. The amide functions ensure better stability during hydrolysis than comparable products known in prior art. The invention also relates to new pharmaceutical, cosmetic, dietetic, or phytosanitary compositions based on the inventive polyamino acids.