Porous, bicontinuous, and cationic polyelectrolyte obtained by high internal phase emulsion polymerization

In this work, a cationic polyelectrolyte was synthesized through oil-in-water high internal phase emulsion polymerization. The porous polymer was obtained using the monomer (4-vinyl benzyl)trimethylammonium chloride and cross-linked with N,N-methylene-bis-acrylamide; additionally, ethylene glycol dimethacrylate (EGDMA) was used as the second cross-linker, which was solubilized in the discontinuous phase leading to a bicontinuous-like HIPE system because of the characteristics of this cross-linker and the phase, where polymerized several effects on the polyHIPE were expected. In this way, the effect of the emulsifier and EGDMA content on the pore size, swelling, and rheological properties was assessed. It was observed that an increased concentration of the emulsifier in the polymerization decreased the pore size, narrowed its size distribution, and diminished the swelling capacity of the polymer. Additionally, the poly (HIPE) displayed a close-cell structure explained by the locus of initiation starting from the droplets of the emulsion. After the addition of EGDMA, the polymer exhibited a major decrease in pore size and a significant decrease in swelling attributed to the polymerized skin layer on the droplet and hydrophobicity provided by the polyEGDMA, respectively. Rheological assays revealed an increase in the complex modulus and shear stress as the pore size decreased, but the addition of EGDMA did not produce an increase in the modulus, as expected. Finally, the sorption capabilities of the cationic porous polymers were evaluated through kinetic and isotherm sorption experiments using the anionic dye Acid Black 24.