A dilute aqueous solution of the temperature-sensitive polymer, poly(vinyl methyl ether) (PVME), was irradiated by a pulsed electron beam in a closed-loop system. At temperatures, below the lower critical solution temperature (LCST), intramolecular crosslinked macromolecules, nanogels, were formed. With increasing radiation dose D the molecular weights M-w increase, whereas the dimensions (radius of gyration R-g, hydrodynamic radius Rh) of the formed nanogels decrease. The structure of the PVME nanogels was analyzed by field emission scanning electron microscopy (FESEM) and globular structures with d= (10-30) nm were observed. The phase-transition temperature of the nanogels, as determined by cloud point measurements, decreases from T-cr=36 degrees C (non-irradiated polymer) to T-cr=29 degrees C (c(p)= 12.5 mM, D = 15 kGy), because of the formation of additional crosslinks and an increase in molecular weights. The same behavior was observed for a pre-irradiated PVME (gamma-irradiation) with higher molecular weight due to intermolecular crosslinks. After pulsed electron beam irradiation the molecular weight again slightly increases whereas the dimension decreases. Above D = 1 kGy the calculated rho-parameter (rho = R-g/R-h) is in the range of rho = 0.5-0.6 that corresponds to freely draining globular structures. (c) 2005 Published by Elsevier Ltd.