Novel water-swellable beads based on an acryloylate polyaspartamide

Spherical polymeric microparticles have been prepared by a reverse-phase suspension polymerization technique. The starting polymer was α,β-poly (N-2-hydroxyethyl)-DL-aspartamide (PHEA) partially functionalised with glycidylmethacrylate (GMA) in order to introduce reactive vinyl groups in the side chain. The PHEA-GMA copolymer obtained (PHG) was cross-linked in a mixture of water/hexane-carbon tetrachloride in the presence of sorbitan trioleate (Span 85) as surfactant and ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine as initiator system. The reaction was also carried out in the presence of N,N′-dimethylacrylamide as comonomer or N,N′-ethylenebisacrylamide as a cross-linking agent. The beads obtained were characterized by Fourier transformIR spectrophotometry, particle size distribution analysis and scanning electron microscopy, which revealed their microporous structure. X-ray diffractometry and differential scanning calorimetry showed the amorphous state and the dependence of the glass-transition temperature on the chemical structure of the samples prepared, respectively. Finally, in order to have information on the water affinity of the networks obtained, swelling measurements were performed. The water regain values and the high rate of swelling demonstrate a remarkable ability of the samples investigated to entrap water molecules. The dependence of aqueous swelling on the degree of cross-linking and the chemical structure of the samples is also shown.