This paper describes the synthesis and characterization of amphipathic diblock copolymers of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO). The synthesis involved the coupling of acyl chloride-terminated PMMA block with methoxy poly(ethylene oxide) (MPEO). Carboxylic acid chloride-terminated PMMA was generated by treating with thionyl chloride the parent carboxylic PMMA, which was prepared by free radical polymerization of methyl methacrylate (MMA) using benzoyl peroxide (BPO) as the initiator and -mercaptopropionic acid (MPA) as the chain transfer agent. The proposed mechanism of MMA polymerization is in good agreement with the experimental results which indicate that as a side reaction nonfunctional (aromatic) counterpart is produced in a small quantity. The coupling of the acyl chloride-terminated PMMA with MPEO was quantitative.