Highly porous polyelectrolyte beads through multiple-emulsion-templating: Synthesis and organic solvent drying efficiency

Abstract

Thus far, emulsion-templated macroporous hydrogels have mostly been produced as monolithic blocks corresponding to the dimensions of the polymerization vessel, while the number of examples of other shapes and dimensions is as yet fairly small. In this article, we report on the double-emulsion-templated synthesis of spherical, cross-linked polyelectrolyte-based hydrogel beads through the sedimentation polymerization of oil-in-water-in-oil (O/W/O) high internal phase emulsions (HIPEs). When a mixture of 2-acrylamido-2-methyl-1-propanesulfonic acid or (3-acrylamidopropyl)-trimethylammonium chloride (AMPS or AMPTMA, ionic monomers) and acrylamide (AAM, a nonionic monomer) was used, the sedimentation polymerization of O/W/O HIPEs resulted in spherical polymerized high internal phase emulsions (polyHIPE) copolymer beads with a throughout open macroporous morphology. A combination of three-dimensionally-interconnected macroporous morphology and small spherical size remarkably improves the swelling and water absorption properties of the beads as dry beads swell to near-equilibrium size within seconds as opposed to hours in the case of monolithic blocks. PolyHIPE beads have a hygroscopic character due to their inherent charges within the macroporous framework. Therefore, the throughout porous morphology and charged functionality of the polyelectrolyte polyHIPE beads allow reversible and rapid water absorption from the tested organic solvents with a water removal efficiency of up to 95%. This work opens a new path to polyHIPE hydrogel engineering, with extremely fast water-absorption capability, which may have promising applications in various fields such as agriculture, horticulture, hygiene products, and daily chemicals.