A novel approach for the fabrication of magnetoactive carbon nanotubes (CNTs) stabilized in aqueous media, involving the combination of carboxylated single-wall carbon nanotubes (SWCNTs) with a new class of methacrylate-based chelating diblock copolymers, is described. More precisely, a well-defined diblock copolymer consisting of hexa(ethylene glycol) methyl ether methacrylate (hydrophilic and thermo-responsive) and 2-(acetoacetoxy)ethyl methacrylate (hydrophobic and metal-chelating) synthesized by reversible addition-fragmentation chain transfer polymerization has been used to prepare polymer-coated magneto-active SWCNTs decorated with iron oxide nanoparticles. Further to the characterization of the compositional and thermal properties using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and thermal gravimetric analysis, assessment of the magnetic characteristics by vibrational sample magnetometry disclosed superparamagnetic behavior at room temperature. The latter, combined with the thermo-responsive properties of the polymeric coating and the unique, inherent properties of the carbon nanotubes may allow for their future exploitation in the biomedical field. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1389-1396, 2011