Porous nanoclay polysulfone composites: A backbone with high pore accessibility for functional modifications

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Microporous, highly charged and cation exchangeable clays are interesting carriers not only for various functional molecules such as cationic dyes, surfactants, proteins, drugs and complexes, but also for water insoluble molecules. In water, swellable nanohectorite derivatives (“laponites”) with dimensions of about 25 nm in diameter and 1 nm in height delaminate to form individual nanoparticles, which proved to be very useful for applications in aqueous dispersions, but less advantageous for the use in filter systems for water treatment, membrane technology, or as catalysts. To immobilize the particles in aqueous environments and still provide accessibility and high cation exchange rates on the clays, we used an inversion process to prepare porous nanoclay polysulfone composites with high clay contents up to 60%. Successful incorporation of the clays in the matrix required clay pre-modifications with reactive silanes such as octyltriethoxysilane or octadecyltriethoxysilane. Interestingly, unmodified laponite can also be used as a template to form a porous polysulfone network due to its leakage in the inversion process. The high accessibility and activity found in composites prepared with a mixture of unmodified and modified laponite particles pave the way for further modifications with functional molecules for various applications. In this study, we characterize the nanoclay polysulfone composites via scanning electron microscopy, nitrogen gas adsorption of the dried composite, and we determine the cation exchange capacity in the wetted state.