PEG20-Tos, or polyethylene glycol 20-tosylate, is an activated PEG derivative primarily used as an intermediate in bioconjugation and PEGylation processes. It enables the attachment of PEG chains to proteins, peptides, and other biomolecules, improving their solubility, stability, circulation time, and reducing immunogenicity in pharmaceutical applications. This makes it valuable for developing PEGylated therapeutics and drug delivery systems. In organic synthesis, it serves as a reagent for introducing hydrophilic PEG groups. While it retains some surfactant-like properties of PEG, such as enhancing solubility and dispersion, its key role is as a niche additive in biochemical and pharmaceutical research rather than general emulsification.