The amine functional group at one end of the PEG linker molecule allows for selective and covalent attachment to other molecules with complementary functional groups, such as carboxylic acids or activated esters, aldehydes and epoxides. The terminal azide functionality reacts with DBCO, BCN or other alkynes under "Click" Chemistry conditions (for example Cu(I) catalyzed alkyne-azide cycloaddition, CuAAC) to form a stable triazole link between the two reaction partners.