Azido-PEG14-t-butyl ester serves as a PROTAC linker from the PEG family, utilized in synthesizing PROTAC molecules. It acts as a click chemistry reagent containing an Azide group, enabling copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with Alkyne-containing molecules. Additionally, it can undergo strain-promoted azide-alkyne cycloaddition (SPAAC) reactions with molecules that have DBCO or BCN groups.