The radio-frequency plasma-initiated polymerization of N-isopropylacrylamide (NIPAM) in the solid state was performed. The isolated linear polymer was characterized by C-13-NMR, H-1-NMR, and Fourier transform infrared spectroscopy, and the effects of selected operational plasma parameters (discharge power and time) on the conversion rates were studied. Reversible transitions at the volume-phase-transition temperatures of the swelled poly(N-isopropylacrylamide) hydrogels were investigated by differential scanning calorimetry. The surface morphologies before and after plasma treatment were followed by scanning electron microscopy. With the obtained X-ray diffraction results, we propose a solid-state plasma polymerization mechanism for the NIPAM. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3311-3320, 2010