β‐Cyclodextrin‐based macroporous monoliths: One‐pot oil‐in‐oil emulsion templating and adsorption

Abstract

AbstractThe ability of β‐cyclodextrin (β‐CD) to form a host–guest complex with relatively hydrophobic molecules such as bisphenol A (BPA), a common wastewater contaminant, has inspired the development of β‐CD‐containing polymers for adsorption applications. For the most part, these polymers are powders, which can limit their applicability. Here, low‐density (~0.1 g cm−3), macroporous monoliths based on unmodified β‐CD were synthesized using emulsion templating. The relatively simple, one‐pot, polyurethane synthesis took place within the external phase of oil‐in‐oil (o/o) high internal phase emulsions (HIPEs) that contained β‐CD and a diisocyanate. The combination of o/o emulsions and a polyurethane reaction enabled the incorporation of relatively high β‐CD contents (up to 63 wt%) and limited the occurrence of the water–isocyanate urea reaction. The resulting open‐cell porous structures varied from an average pore size of 5.0 μm (lower surfactant content) to the typical structure associated with polyHIPEs (higher surfactant content), voids of ~50 μm and interconnecting holes ranging from submicrometer to ~2 μm. The compressive mechanical behaviors of the easily handled monoliths were similar to those of flexible foams, reaching strains of 70% without failure. The BPA adsorption capacities, up to 117.7 mg g−1, may make these monoliths advantageous for adsorption applications.