In this study, a random copolymer of N-isopropylacrylamide and N-vinylpyrrolidone [poly(NIPAM-co-NVP)] having a thermoresponsive character was prepared by a radiation copolymerization method. Poly(ethylene glycol), PEG 4000, was included in the copolymerization recipe to increase the thermoresponsivity of the resultant copolymeric structures. NIPAM-co-NVP copolymers with different thermoresponsive properties were obtained by changing the initial NIPAM/NVP mol ratio, total monomer, and PEG 4000 concentrations.