Propargyl-PEG3-bromide is widely used in bioconjugation and click chemistry applications. Its propargyl group enables efficient reactions with azides via copper-catalyzed azide-alkyne cycloaddition (CuAAC), making it valuable for labeling biomolecules such as proteins, peptides, and nucleic acids. The PEG3 spacer enhances solubility and reduces steric hindrance, improving reaction efficiency. It is also employed in the synthesis of drug delivery systems, where it facilitates the attachment of targeting ligands or therapeutic agents. Additionally, it serves as a key intermediate in the development of functionalized materials for research in nanotechnology and biomedical sciences.