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

The ability of beta-cyclodextrin (beta-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 beta-CD-containing polymers for adsorption applications. For the most part, these polymers are powders, which can limit their applicability. Here, low-density (similar to 0.1 g cm(-3)), macroporous monoliths based on unmodified beta-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 beta-CD and a diisocyanate. The combination of o/o emulsions and a polyurethane reaction enabled the incorporation of relatively high beta-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 mu m (lower surfactant content) to the typical structure associated with polyHIPEs (higher surfactant content), voids of similar to 50 mu m and interconnecting holes ranging from submicrometer to similar to 2 mu m. 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.