Grafted temperature-sensitive poly(N-vinylcaprolactam), PVCL, microgel, particles have been prepared. The grafting has been accomplished using an amphiphilic macromonomer consisting of a hydrocarbon segment and a poly(ethylene oxide), PEG, segment. The water-soluble amphiphilic macromonomer has been synthesized and utilized in two different cases. In the first case, the grafted particles were prepared using macromonomers as reactive emulgators in emulsion copolymerization. In the second case the PVCL particles were first synthesized in an emulsion stabilized with SDS, and then, the microgel particles swollen with monomers were postmodified with amphiphilic macromonomers. Properties of the grafted nanoparticles in water were investigated by static and dynamic Light scattering, as well as by H-1 NMR relaxation and diffusion measurements. All the polymers show the LCST behavior typical to PVCL, and they collapse upon heating. For the particles prepared in one step in an emulsion stabilized by the macromonomer, the collapse was discontinuous and took place in a very narrow temperature range. When the particles were prepared in two steps, the grafts were observed to change the particle size as well as the critical temperature of the collapse. In the latter case the thermal transition was much more gradual than in the former one. This is probably due to a difference in the number of electric charges in the polymer particles, originating from the initiator and SDS.