Propargyl-PEG4-C2-acid is widely used in bioconjugation and click chemistry applications due to its terminal alkyne group, which enables efficient and selective reactions with azide-containing molecules. This compound is particularly valuable in the development of drug delivery systems, where it facilitates the attachment of targeting ligands or therapeutic agents to biocompatible carriers like PEGylated nanoparticles. It is also employed in the synthesis of peptide and protein conjugates, enabling the study of biomolecular interactions and the creation of novel biopharmaceuticals. Additionally, its PEG spacer enhances solubility and reduces immunogenicity, making it suitable for in vivo applications in diagnostics and therapeutics. In material science, it is used to modify surfaces or polymers, enabling the creation of functionalized materials for biosensors or tissue engineering scaffolds.