A thermo-sensitive hydrogel was synthesized by irradiation of an aqueous solution of poly(methyl vinyl ether) (PMVE) with electrons. At high polymer concentration a bulk gel was formed. Irradiation of diluted polymer solution at a temperature above the phase transition temperature conserves the structure of the polymer in the phase-separated state. The micro-particles formed under irradiation conditions possess also typical thermo-sensitive properties. Their diameter roughly amounts to 300-500 nm in the swollen state depending on the temperature of the solution. Static and dynamic light scattering were used to determine the dimension of the formed particles. The dry, swollen, and shrunk state were structurally characterized by field emission scanning electron microscopy (FESEM).