Soft, Elastic Macroporous Monolith by Templating High Internal Phase Emulsions with Aminoclay: Preparation, Pore Structure and Use for Enzyme Immobilization

We describe the preparation of macroporous monolithic structures by templating high internal phase emulsions with platelike aminoclay nanoparticles. We demonstrate that choice of surfactant affords control over pore structure within the monolith. Scanning electron microscopy shows that using anionic surfactant (sodium dodecyl sulfate) leads to the formation of closed pores that template oil droplets in the emulsion, whereas cationic surfactant (cetyltrimethylammonium bromide) results in the formation of a network-like structure that does not directly replicate the oil droplets. Of particular interest are monoliths prepared using nonionic surfactant (Pluronic F127); this results in the formation of an interconnected open pore monolith, which is soft, and exhibits remarkable elasticity: they can recover from compressive strains as large as 80%. As a consequence of this, these monoliths are robust and do not crack on air drying at room temperature despite experiencing large (≈ 45%) volume shrinkage. We intercalate glucose oxidase enzyme in the aminoclay and use these constructs to prepare monoliths with an interconnected porous structure. We demonstrate monolith porosity can be tuned by increasing the oil volume fraction. Increasing the oil fraction in the emulsion from 74 to 82.6% increased the monolith porosity from 72.5 to 84.4%, resulting in an increase in enzyme activity. Enzymes encapsulated in the monoliths are stable against chaotropic solvents and changes in pH.