Hydroxyethylmethacrylate (HEMA), hydroxypropylmethacrylate (HPMA) and trimethylolpropanetrymethacrylate (TMPTM) are copolymerised by gamma-irradiation to give five potentially amphiphilic gel-type resins. The molar fraction of TMPTM (the cross-linker) is constant (4 mol%) while the five resins are featured by different HEMA/HPMA molar ratios (96/0, 68/28, 48/48, 28/68 and 0/96, respectively). The swollen state morphology of the five materials is investigated by means of inverse steric exclusion chromatography (ISEC) and electron spin resonance (ESR) spectroscopy based on the spin-probe TEMPONE (2,2,6,6-tetramethyl-4-oxo-1-oxyl-piperidine) both in water and tetrahydrofuran (THF). In THF, swelling and accessibility of the polymer network increase with the increase in HPMA content. In contrast, the five materials are poorly swollen by water and no apparent dependence of swelling on HPMA/HEMA ratio is detected. (C) 2002 Elsevier Science BN. All rights reserved.