Azido-PEG36-NHS ester is a PROTAC linker belonging to the PEG family, useful in the synthesis of PROTAC molecules. As a click chemistry reagent, it contains an azide group, facilitating copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with molecules containing alkyne groups. It also participates in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules containing DBCO or BCN groups.