Well-defined amphiphilic polymethylene-b-poly (acrylicacid) diblock copolymers have been synthesized via a new strategy combining polyhomologation and atom transfer radical polymerization (ATRP). Hydroxyl-terminated polymethylenes (PM-OH) with different molecular weights and narrow molecular weight distribution are obtained through the polyhomologation of dimethylsulfoxonium methylides following quantitative oxidation via trimethylamine-N-oxide dihydrate. Subsequently, polymethylene-based macroinitiators (PM-MIs Mn = 1,300 g mol-1 [Mw/Mn = 1.11] and Mn = 3,300 g mol-1 [Mw/Mn = 1.04]) are synthesized by transformation of terminal hydroxyl group of PM-OH to a-haloester in similar to 100% conversion. ATRPs of tert-butyl acrylate (t-BuA) are then carried out using PM-MIs as initiator to construct PM-b-P(t-BuA) diblock copolymers with controllable molecular weight (Mn = 8,80015,800 g mol-1 Mw/Mn = 1.041.09) and different weight ratio of PM/P(t-BuA) segment (1:1.71:11.2). The amphiphilic PM-b-PAA diblock copolymers are finally prepared by hydrolysis of PM-b-P(t-BuA) copolymers and their self-assembly behavior in water is preliminarily investigated via the determination of critical micelle concentrations, dynamic light scattering, and transmission electron microscope (TEM). (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012