Design of polymer nanofiber systems for the immobilization of homogeneous catalysts - Preparation and leaching studies

In this paper a novel general concept for the immobilization of catalysts is presented. It will be shown that catalysts covalently bound to low-molecular weight polystyrene (Mn > 4000 g/mol) can be immobilized into high molecular weight polystyrene nanofibers using the electrospinning process. The immobilized catalyst-oligostyrene conjugates are well dispersed within the fibers as shown by DSC and X-ray studies. In DMSO, the oligostyrene tails of the catalysts suppress the leaching of the catalysts out of the fibers into the solution for thermodynamic reasons. Leaching studies are conducted using naphthalene-conjugated oligostyrenes using fluorescence spectroscopy. The naphthalene-polystyrene conjugates with defined molecular weight are readily prepared using nitroxide-mediated radical polymerization (NMP). As a model catalyst system, proline-polystyrene conjugates are synthesized by NMP to study catalyst leaching out of the polystyrene nanofibers used as a catalyst matrix.