The swelling and porosity change of the pentaerythritol triacrylate (PENTA) homopolymer and PENTA-butyl acrylate (BA) copolymers were investigated as a function of PENTA content (80, 60, 40 and 20 wt%). Polymers were synthesized by the suspension polymerization method using cyclohexanol and 2-ethylhexanol as inert diluents. The solubility parameter of poly(PENTA) (18.2 MPa1/2) was estimated by swelling in the heptane and tetraline mixture. From the swelling of copolymers in the solvents toluene, THF, benzene and dioxane, one may conclude that the swelling of copolymers is not only a function of the solubility parameter of the solvent. The presence of hydroxyl groups in PENTA results in the highest sorption of dioxane. The porosity of copolymers in the swollen state is similar in all solvents. The porosity in the swollen state was characterized by inverse size exclusion chromatography (ISEC) using THF (polystyrene standards) and water (dextrane standards). Swelling in good solvents proceeds with an enlargement of the bead volume, hence the pore volume after swelling in THF is greater than in water in which the influence of hydroxyl groups leads to swelling of triacrylate segments at the cost of the pore volume. Copolymers synthesized with the higher diluents:monomer ratio are hydrogels with the ability to change their porosity, pore diameter and volume of beads. During drying, their pores collapse. (C) 1997 Elsevier Science Ltd.