Poly(ethylene glycol)s (PEGs) are the most used polymers in biomedicine, and their so-called “stealth” effects are the “gold standard” for biomaterials. However, the polydispersity in regular PEGs hampers their biomedical application, especially in modification of small molecular drugs (SMDs). To address this issue, many synthetic strategies for monodisperse PEGs (M-PEGs) have recently been developed. More importantly, M-PEGs have been successfully employed to modify SMDs, and the crucial roles of M-PEGs in PEGylated SMDs have been discover...