AbstractPorous poly(2‐hydroxyethyl methacrylate) (PHEMA) beads cross‐linked with ethylene glycol dimethacrylate (EGDM) were prepared by the suspension polymerization of the monomers in the presence of cyclohexanol or toluene as the diluents. A 20 aqueous NaCl solution containing MgCl2· 6H2O, bentonite, and gelatine was used as the water phase. In this way, spherical, highly swellable, and/or porous copolymer beads of sizes 0.1–1.0 mm could be synthesized at EGDM contents higher than 20 mol . The copolymers formed in cyclohexanol, compared to those prepared in the absence of a diluent, exhibit a larger degree of volume swelling in water, indicating that most of the diluent remains in the gel phase throughout the copolymerization. Contrarily, toluene induces porous structures even at a very low degree of cross‐linking (41 porosity at 2 mol EGDM). An interesting feature of HEMA–EGDM copolymerization in toluene is that the pore volume of the networks increases with increasing EGDM concentration up to 20 mol , but it decreases again as the EGDM concentration further increases. The results can be explained with the differences in the solvating conditions of the copolymers depending on their EGD
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