Well-defined polymethylene-block-polystyrene (PM-b-PS) diblock copolymers were synthesized via a combination of polyhomologation of ylides and reversible addition-fragmentation chain-transfer (RAFT) polymerization of styrene. Trithiocarbonate-terminated polymethylenes (PM-TTCB) (Mn=1400 g mol-1; Mw/Mn=1.09 and Mn=2100 g mol-1; Mw/Mn=1.20) were obtained via an esterification of S-1-dodecyl-S-(,-dimethyl--acetate) trithiocarbonate with hydroxyl-terminated polymethylene synthesized via polyhomologation of ylides followed by oxidation. Then, a series of PM-b-PS (Mn=5500-34,000 g mol-1; Mw/Mn=1.12-1.25) diblock copolymers were obtained by RAFT polymerization of styrene using PM-TTCB as a macromolecular chain-transfer agent. The chain structures of all the polymers were characterized by proton nuclear magnetic resonance (1H NMR), gel permeation chromatography, and Fourier transform infrared spectroscopy. The thiocarbonylthio end-group of PM-b-PS was transformed into thiol group by aminolysis and confirmed by UV-vis spectroscopy. In addition, microfibers and microspheres of such diblock copolymers were fabricated by electrospinning process and observed by scanning electron microscopy (SEM). (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2892-2899