Swellable ethylene glycol dimethacrylate-hydroxyethylmethacrylate copolymer beads

In this study, swellable poly(EGDMA/HEMA) beads in the size range of 30-170 mu m with different size distributions were produced by suspension copolymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) in aqueous media. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. The diluent, i.e. toluene was included in the recipe of the second group of copolymerizations. The beads were characterized by optical microscopy, FTIR and FTIR-DRS. Crosslinked, transparent, nonporous and swellable (up to a swelling ratio of 31.2%) poly(EGDMA/HEMA) beads were obtained in which there was no toluene in the recipe. While copolymerizations with toluene provided swellable (up to a swelling ratio of 57.1%), opaque, porous and crosslinked copolymer beads. In the polymerization (without toluene) HEMA is mainly incorporated on the outer layers (near surface) of the beads. In this case, increase in the EGDMA/HEMA ratio resulted larger beads with wider size distributions, and with lower swellabilities. The porosity of the dry copolymer beads were studied with mercury pycnometric method. Incorporation of toluene within the recipe (in the modified polymerization) caused pronounced effects both on bead size and swellability. Larger beads with broader size distributions, with higher swellabilities were obtained when the relative amount of toluene increased.