458604 Multifunctional Magnetic Nanoparticles By Surface Initiated Atom Transfer Radical Polymerization

Wednesday, November 16, 2016: 9:10 AM
Golden Gate (Hotel Nikko San Francisco)
Martin Zeltner, ETH Zurich, 8093 Zurich, Switzerland, Robert N. Grass, Institute for Chemical and Bioengineering, ETH-Zürich, Zürich, Switzerland, Corinne Hofer, ETH Zurich, Institute for Chemical and Bioengineering, ETH Zurich, Zurich, Switzerland, Elia Schneider, ETH Zurich Institute for Chemical and Bioengineering, ETH Zurich, Zurich and Wendelin J. Stark, Institute for Chemical- and Bioengineering, ETH Zurich, Zurich, Switzerland

Superparamagnetic and ferromagnetic nanoparticles are of huge interest in various areas of science (e.g. chemistry, biology, bio-chemistry, medicine, sensor technology)1. The requirements for particles are as multifaceted as the areas, in which they are applied. Nanoparticles enjoy great popularity as particles at the nanoscale exhibit a favorable surface to volume ration in comparison to the same bulk material. However, this property is not that valuable, if other requirements do not fit.

For chemical applications, the particles most often have to be quickly separable, inert and stable against harsh environment like temperature, challenging pH-values and solvents.2,3 In contrast to this, medical and biological applications usually afford dispersion stability in aqueous solutions and compatibility with biological relevant media (e.g. phosphate buffered saline (PBS) or Dulbecco’s modified eagle’s medium (DMEM))4. For sensor application, the requirements to the magnetic nanoparticles contain huge dispersion stability, a high saturation magnetization and the possibility for further modification (e.g. attachment of a target substance etc.)4,5,6. Requirements to the magnetic nanoparticles which are highly demanded, often contain multiple combinations of different properties. This afford smart materials which contains amphiphilic character. Such smart materials can for example change the properties by an external trigger (temperature, pH, gas)7.

Most of the different requirements can be achieved using carbon coated ferromagnetic nanoparticles as a platform. The graphene-like layers protect the magnetic metal core from oxidation and allows the covalent attachment of chemical functionalities via diazonium chemistry8. There are numerous functionalities which can be implemented by this approach. Amongst them, alcohol-, amine-, carboxy-, azide- or an initiator moiety for atom transfer radical polymerization (ATRP) can be listed, just to mention a few7,9,10. Adsorption of a polymer can usually not satisfy the requirements, as adsorbed polymers tend to form only single layers and desorption frequently occurs.

In contrast to this, surface initiated ATRP (SI-ATRP: polymer-growth from the surface) is suitable with a plethora of different monomers (desired functionality) and the polymerization can be well controlled (layer thickness and block-co-polymerization)4,11. Thus SI-ATRP gives the toolbox for various modification of the surface that allows achievement of several desired requirements.

Using charged monomers (e.g. 3-Sulfopropyl methacrylate potassium salt (SPM) or 3-(Methacryloylamino)propyl]trimethylammonium chloride (MAPTAC)) leads to highly stable dispersions in aqueous solutions. The stability can be tuned by the number of repeating units4,6. Using poly(ethylene glycol) methacrylate (PEGMA) as monomer the highly lipophilic graphene layers can be turned into hydrophilic and antifouling surfaces12. The use of glycidyl methacrylate (GMA) gives access to post-modification by epoxide ring opening.4 Most challenging modifications require amphiphilic properties (dispersion stability vs. fast separation or lipophilicity vs. hydrophilicity). Such requirements need a coating with smart polymers, which can change their properties upon external trigger (temperature, pH etc.). By using N-isopropylacrylamine (NIPAM) as building block, the particles can reversibly change between hydrophilic and hydrophobic upon temperature change7. Here the promising potential of SI-ATRP on magnetic nanoparticles in terms of designing a desired nanomaterial for chemical, biological and medical applications is shown13.

[1] A.H. Lu, E.L. Salabas, F. Schueth, Angew. Chem. Int. Ed, 2007, 46, 1222.

[2] A. Schaetz, O. Reiser, W.J. Stark, Chem. Eur. J., 2010, 16, 8950.

[3] Elia M. Schneider, Martin Zeltner, Niklaus Kranzlin, Robert N. Grass, and Wendelin J. Stark, Chem. Commun., 2015, 51, 10695.

[4] C.J. Hofer, V. Zlateski, P.R. Stoessel, D. Paunescu, E. M. Schneider, R.N. Grass, M.Zeltner, W.J.Stark, Chem. Comm., 2015, 51, 1825.

[5] Q. A. Pankhurst, J. Connolly, S. K. Jones and J. Dobson, J. Phys. D. Appl. Phys., 2003, 36, R167.

[6] M. Zeltner, R.N. Grass, A. Schaetz, S.B. Bubenhofer, N.A. Luechinger, W.J. Stark, J. Mater. Chem., 2012, 22, 12064.

[7] M. Zeltner, A. Schaetz, M.L. Hefti, W.J. Stark, J. Mater. Chem., 2011, 21, 2991.

[8] Robert N. Grass, Evagelos K. Athanassiou, and Wendelin J. Stark, Angew. Chem. Int. ed., 2007, 4909.

[9] Alexander Schatz, Robert N. Grass, Wendelin J. Stark, and Oliver Reiser, Chem. Eur. J., 2008,27,8262.

[10]  Chun Ghee Tan, and Robert N. Grass, Chem.Commun., 2008, 36, 4297.

[11] R. Barbey, L.Lavanant, D. Paripovic, N. Schuwer, C. Sugnaux, S. Tugulu, H.A. Klok, Chem. Rev., 2009, 109, 5437.

[12] Elia M. Schneider, Martin Zeltner, Vladimir Zlateski, Robert N. Grass, and Wendelin J. Stark, Chem. Commun., 2016, 52,938.

[13] Tong Bu, Tamotsu Zako, Martin Zeltner, Karin M. Sörgjerd, Christoph M. Schumacher, Corinne J. Hofer, Wendelin J. Stark, and Mizuo Maeda, J. Mater. Chem.B, 2015, 16, 3351.

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