Water-swellable hydrophobic porous copolymers based on divinylbenzene and methyl acrylate: Preparation and water-swelling behavior

Porous copolymers based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared by suspension polymerization in the presence of toluene as porogen. By using purified DVB (98.8%), the resulting MA/DVB copolymers with a wide range of DVB contents were found to be able to swell in water directly, although both the homopolymers derived from DVB and MA are hydrophobic. The amounts of DVB and MA in the copolymers affect the water-swelling behavior profoundly. However, the direct swelling in water occurs only after the DVB or MA content reaches a critical value, and the effect of the MA content will be significant only when the DVB content is at a high level. The latter observation reflects the combined effect of the cross-linking density and the polymer polarity on the swelling ability of the MA/DVB copolymers in water. The nature of the direct swelling of these hydrophobic porous copolymers in water was discussed by considering both factors: the existence of the inner stresses in the strained polymer network and the weak interaction between polymer and water that is negligible in the case of the conventional hydrophobic polymers.