Multiblock polymers with a poly(ethylene glycol) (PEG) block are attractive candidates for biomedical applications because of their favorable properties regarding biocompatibility and hydrophilicity. However, the synthesis of PEGylated multiblock polymers (>= 4 blocks) is often considered to be challenging and time consuming. Herein, we describe a new approach for the rapid synthesis of PEGylated multiblock polymers with precisely defined and high-order chemical structures based on PEG macroinitiators via aqueous single electron transfer living radical polymerization (SET-LRP) in which 2-hydroxyethyl acrylate (HEA) is used as an exemplary monomer. Kinetic experiments were performed for the synthesis of PEGylated diblock polymers with a range of number-averaged molecular weights (DPn = 10-100) proceeding to full monomer conversion within 20 min and exhibiting very narrow molecular weight distribution (D <= 1.07). This optimized approach was subsequently utilized to perform in situ chain extensions with another aliquot of the monomer at a quantitative or near quantitative amount, yielding a wide range of PEGylated multiblock polymers of low dispersity (D <= 1.19) and quantitative yields >99% for each monomer addition, thus circumventing the requirements for intermediate purification, within 40 min of polymerization per block. This synthesis approach is environmentally friendly and fully translational and thus can further contribute to the design of high-precision polymers with tailorable block compositions and polymer topologies, which is highly attractive for a wide range of applications in nanotechnology.