ABSTRACT:The swelling capacity of porous styrene-divinylbenzene (DVB) copolymers in water was studied by displacing methanol from the swollen polymer. The copolymers with different amounts of DVB were prepared in the presence of solvents with different solvating powers as inert diluents. Using a solvating solvent or its mixture with a nonsolvent as diluent, most of the obtained copolymers increase their volume in water, and the increase in volume becomes more significant with increasing the degree of crosslinking in some range of the DVB contents. The swelling capacity in water for the same copolymers with a high degree of crosslinking is linearly dependent on the dilution degree in the initial reaction mixture, to some extent. The unusual swelling behaviors in water were explained by the inner strain, which existed mainly in the less crosslinked domains between the highly crosslinked microgel particles, which are released in the course of swelling of the copolymers.

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Porous copolymers based on alkyl methacrylate esters (AMA) were prepared in the presence of toluene as the inert diluent, and their swelling properties in water were investigated by measuring the water uptake of the copolymers with or without being pretreated with methanol. With ethylene glycol dimethacrylate (EGDM) being used as the crosslinking agent, the obtained AMA/EGDM copolymers, regardless of their inherent hydrophobic nature, were found to be able to swell in water directly. The swelling was negligible in the lower degree of crosslinking region. However, once it increased to a value beyond a certain EGDM percentage, the swelling transition occurred, and the water uptake, which was measured by direct contact of the copolymers with water for all three kinds of AMA/EGDM copolymers based on methyl MA (MMA), ethyl MA (EMA), and butyl MA (BMA), reached very high values. The direct swelling of highly crosslinked AMA/EGDM copolymers in water was very fast at the beginning of the swelling with the swelling rate order of MMA/EGDM > EMA/EGDM > BMA/EGDM, but thereafter it progressed very slowly with most swelling being achieved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 250–258, 2000

ABSTRACT:Hydrophobic, but water-swellable, porous copolymer resins composed of divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDM) or ethylene glycol diacrylate (EGDA) were prepared by using purified DVB (98.8%) in the presence of toluene as porogen. The EGDM/ DVB resins thus obtained, whose polarity was nearly identical to that of the resins based on DVB and methyl methacrylate (MMA) at the same DVB levels, were water-swellable by direct contact with water up to a DVB content of 64%, whereas the latter did not swell in water at any DVB levels. EGDA is also hydrophobic, but with a polarity greater than that of EGDM. As a result, the EGDA/DVB resins were more water swellable than EGDM/DVB resins, and could also be prepared as water-swellable materials by using technical DVB (79.3%), besides the use of the purified DVB. All these results were explained on the basis of the network rigidity (crosslinking density) and the polymer polarity of the resins that were formed in the presence of a well-solvating porogenic solvent.

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