N-(Propargyl-PEG2)-N-bis(PEG1-alcohol) is a branched PEG derivative with two terminal hydroxy groups and a propargyl group. The hydroxy groups enables further derivatization or replacement with other reactive functional groups. The propargyl group can be reacted with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield a stable triazole linkage.