Used as a key intermediate in the synthesis of PEGylated pharmaceuticals, enabling controlled drug release and improved solubility of therapeutic compounds. Its long PEG chain enhances biocompatibility and prolongs circulation time in vivo, making it valuable in developing biopharmaceuticals and targeted delivery systems. The t-butyl ester group allows for selective deprotection during conjugation, facilitating precise modification of active molecules. Commonly employed in the preparation of antibody-drug conjugates (ADCs) and functionalized polymers for biomedical research.