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submitted on 06.02.2020, 14:41 and posted on 07.02.2020, 07:15by Dennis Kollofrath, Marcel Geppert, Sebastian Polarz
The development of drugs for birth-control has changed society, and they are used by billions of woman on an every day basis. As for every mass product, there are problems associated with the waste it causes. One has found that residues of hormones in the urine of woman cannot be removed sufficiently from waste-water and this, in-turn, has already observable and undesired consequences in the biosphere. Apart from the removal of drugs, one is in general seeking new methods for the removal of hydrophobic impurities from waste-water. An ideal system would quantitatively take up the impurity, entrap it followed by preferably simple separation. Finally, one wants to reuse the absorbent, which implies the possibility for regeneration and recycling. Such as complex set of tasks requires a relatively complex materials architecture. Functional organic polymers with high affinity towards the drug, with stable open porosity and high surface area, stimuli-responsive properties and in the form of colloidal dispersions could do the job. Unfortunately, such a system does not exist. We solved this problem by generating mesoporous organosilica nanoparticles, which are monomers at the same time. Initiation of the polymerization reaction by surface-bound pore-walls leads to the formation of a special type of block-copolymer. The pore-walls are covered by the polymer, which cannot leach. An orthogonal modification was achieved by modification of the external surfaces of the particles with a thermoresponsive polymer by click-chemistry. The final core-shell system was able to remove hydrophobic molecules such as the hormone progesterone from water. A change of temperature induces the collapse of the thermoresponsive polymer, which closes the pores and induces aggregation of the particles. After separation of the particles, and thus also the entrapped impurity, from the solvent, one can re-open the pores, which leads to a release of the adsorbed compound(s).