(471d) Amphiphilic Metal Nanomagnets: Towards Magnetic Soaps and Recyclable Detergents

Magnetic nanoparticles are of increasing interest in various areas of contemporary technologies, emphasizing on drug delivery, catalysis, separation of biological species or wastewater purification mentioning just the most recent interests. Schmidt et al.[1] described dispersions of magnetic nanoparticles as an attractive alternative for separation applications because of their high surface area, which can be functionalized in numerous ways. Unfortunately, magnetic nanoparticles tend to agglomerate and grow to micronsized agglomerates due to the magnetic attraction. It would be strongly favorable to control the agglomeration by an external factor e.g. by using an amphiphilic polymer. Poly-N-Isopropylacrylamide (PNIPAM) is such an amphiphilic polymer with a switch temperature close to physiological conditions[2]. Therefore, we covalently bound PNIPAM to the surface of carbon coated metal nanoparticles, which were prepared by an industrial relevant flame spray synthesis process[3]. Via diazo-coupling, an anchor group can be linked covalently to the graphene on the surface of the particles[4]. The NIPAM was grafted to the nanomagnets by atom transfer radical polymerization (ATRP) in order to achieving polymer brushes[1]. These brushes counteract the magnetic attraction force by sterical hindrance. The resulting PNIPAM modified cobalt particles showed amphiphilic properties, depending on the temperature due to the fact that the polymer is subject to hydrophobic effect. Within this study, we showed that the amphiphilic particles translocated reversibly from hydrophilic to hydrophobic phases upon heating and cooling. We propose this effect for the use as magnetic soaps or as recyclable detergent.

References:

[1] Gelbrich, T., M. Feyen, and A.M. Schmidt, Macromolecules, 2006.

[2] Alarcon, C.D.H., S. Pennadam, and C. Alexander, Chem. Soc. Rev., 2005.

[3] Grass, R.N. and W.J. Stark, J.Mater. Chem. 2006.

[4] Grass, R.N., E.K. Athanassiou, and W.J. Stark, Angew. Chem. Int. Ed., 2007.