A cyclic carbonate monomer, including: wherein R1, R2, and R3 are independently selected from the group consisting of H, linear or branched, substituted or unsubstituted alkyl; R10 is a connecting group selected from the group consisting of linear or branched, substituted or unsubstituted alkyl, heteroalkyl, cycloalkyl, heterocyclic, aryl and heteroaryl; R4 is an optional bridging group selected from the group consisting of linear or branched, substituted or unsubstituted alkyl, heteroalkyl, cycloalkyl, heterocyclic, aryl and heteroaryl; Z is selected from the group consisting of O, NH, NR, and S; G is a guanidine group; and P is a protecting group.The cylic carbonate monomer can be reacted with an initiator including a drug, drug candidate, probe or other molecule of interest to form an oligomer with the molecule of interest attached to one end of a carbonate backbone and guanidine groups attached to the carbonate backbone.