Thalidomide-O-PEG4-azide is primarily utilized in the field of targeted drug delivery and proteolysis-targeting chimeras (PROTACs). Its structure allows it to act as a linker, connecting thalidomide, a molecule known for its ability to bind cereblon (CRBN), with other therapeutic agents or targeting molecules. This enables the selective degradation of specific proteins, making it valuable in cancer research and treatment. Additionally, the azide group facilitates click chemistry, allowing for efficient conjugation with biomolecules, which is useful in bioconjugation studies and the development of novel therapeutics. Its application extends to chemical biology for studying protein interactions and cellular pathways.