23-Azido-3,6,9,12,15,18,21-heptaoxatricosan-1-amine (Azide-PEG7-Amine, N3-PEG7-NH2) is a mono-dispersed heterofunctional PEG with an azide and an amine group on the PEG ends. It is a useful crosslinking reagent with a PEG spacer. Azide can be used for molecule conjugation by click chemistry, and amine can react with carboxylic acid or NHS ester. The product is typically provided in HCl salt form. Azide-PEG-Amine may be used to for bioconjugation, drug delivery, PEG hydrogel, crosslinker, and surface functionalization.