The present invention relates to the field of perfumery. More particularly, it concerns co-polymers, derived from aspartic acid and comprising at least one alpha- or beta-aspartic acid derivative capable of liberating an active molecule such as, for example, an alpha, beta-unsaturated ketone or aldehyde. The present invention concerns also the use of polymers or co-polymers in perfumery as part of a perfuming or malodor counteracting composition, as well as the perfuming compositions or perfumed articles comprising the invention's compounds.