Azide PEG or PEG azide is widely used in “Click” chemistry, the particular example
of the Cu(I) catalyzed reaction of the azide and a terminal acetylene; and b) the
Staudinger ligation using functionalized aryl phosphines to couple the azide in a
covalent fashion to form amides.
The attraction of the azide functionality is its low reactivity and high stability
under most conditions, especially where other conjugating functionalities have to be
used due to their limited stability, or when careful control of variables, like pH,
are required in order to insure high yielding reactions.