Poly(ethylene oxide) (PEO) macromonomers (1 and 2) carrying a methyl, n-butyl, tert-butyl, n-octyl, or n-octadecyl group as the omega-end and a p-vinylbenzyl or methacryloyl group as the alpha-end were prepared, and their radical polymerizations in water were found to occur unusually rapidly as a result of their organization into micelles. The micelle sizes were estimated with the nonpolymerizable macromonomer models (3 and 4) by laser light scattering measurements. Significant effects of omega-alkyl groups and the PEO chain lengths on the polymerizability were observed and found to parallel the molecular density of the corresponding model, measured by the degree of aggregation (m) divided by the micelle volume (V(m)). The hydrophobic alpha-ends as polymerizing groups are very likely to be concentrated and organized in the micelle core, with the hydrophilic PEO chains coiling in the surrounding shell, allowing a very rapid polymerization to an amphiphilic comb polymer of a very high molecular weight.