Used primarily as a hydrophilic linker in pharmaceutical and polymer chemistry. Its oligoethylene glycol structure provides water solubility and flexibility, making it ideal for bioconjugation, especially in antibody-drug conjugates (ADCs) and targeted drug delivery systems. The terminal hydroxyl group allows further functionalization, enabling attachment to payloads or targeting moieties. Also employed in surface modification to reduce protein adsorption and improve biocompatibility of medical devices. Commonly found in PEGylation reagents where controlled release and enhanced pharmacokinetics are required.