Bis-PEG18-t-butyl ester is a symmetric bifunctional PEG derivative. Its core structure consists of a PEG18 chain modified with tert-butyl ester groups (-COOtBu) at both ends, with a molecular weight of approximately 1000-2000 Da. The production process employs esterification, using methacrylic acid compounds and 1-octadecanol as raw materials. The reaction is refluxed under the action of an acidic catalyst (such as p-toluenesulfonic acid), followed by purification to obtain a high-purity product (≥95%). Due to its defined molecular weight, symmetric structure, and tert-butyl protecting group characteristics, this reagent is widely used in fields such as drug delivery system construction, PROTAC molecule scaffold design, and biomaterial surface modification. It can achieve functions such as drug controlled release, protein degradation, and reduced immunogenicity.