PENTAERYTHRITOL TRIACRYLATE-HOMOPOLYMER AND ITS COPOLYMERS WITH BUTYLACRYLATE

The swelling and porosity change of the pentaerythritol triacrylate (P ENTA) homopolymer and PENTA-butyl acrylate (BA) copolymers were invest igated as a function of PENTA content (80, 60, 40 and 20 wt%). Polymer s were synthesized by the suspension polymerization method using cyclo hexanol 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 solvent s toluene, THF, benzene and dioxane, one may conclude that the swellin g of copolymers is not only a function of the solubility parameter of the solvent. The presence of hydroxyl groups in PENTA results in the h ighest sorption of dioxane. The porosity of copolymers in the swollen state is similar in all solvents. The porosity in the swollen state wa s characterized by inverse size exclusion chromatography (ISEC) using THF (polystyrene standards) and water (dextrane standards). Swelling i n good solvents proceeds with an enlargement of the bead volume, hence the pore volume after swelling in THF is greater than in water in whi ch the influence of hydroxyl groups leads to swelling of triacrylate s egments at the cost of the pore volume. Copolymers synthesized with th e higher diluents:monomer ratio are hydrogels with the ability to chan ge their porosity, pore diameter and volume of beads. During drying, t heir pores collapse. (C) 1997 Elsevier Science Ltd.