Magnetic force microscopic images of nanometer-sized polyradical particles

Nanometer-sized polymer particles bearing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radicals were prepared. The emulsifier-free emulsion polymerization of methacrylic acid, methyl methacrylate, and methylenebisacrylamide and the following introduction of the TEMPO moiety produced polyradical particles with different spin concentrations. The TEMPO-combined particle was also prepared in one step by the anionic dispersion polymerization of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl. The position and horizontal shape in the atomic and magnetic force microscopic images of the polyradical particle coincided with each other. The vertical scale of the magnetic image responded to the spin concentration of the particle. The particle beating the radicals on its surface gave a hollow dot image.