Article abstract


Nature Materials 8, 354 - 359 (2009)
Published online: 22 March 2009 | doi:10.1038/nmat2404

Subject Categories: Nanoscale materials | Computation, modelling and theory | Polymers

Anisotropic self-assembly of spherical polymer-grafted nanoparticles

Pinar Akcora1, Hongjun Liu1, Sanat K. Kumar1, Joseph Moll2, Yu Li3, Brian C. Benicewicz3, Linda S. Schadler4, Devrim Acehan5, Athanassios Z. Panagiotopoulos6, Victor Pryamitsyn7, Venkat Ganesan7, Jan Ilavsky8, Pappanan Thiyagarajan8, Ralph H. Colby9 & Jack F. Douglas10


It is easy to understand the self-assembly of particles with anisotropic shapes or interactions (for example, cobalt nanoparticles or proteins) into highly extended structures. However, there is no experimentally established strategy for creating a range of anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles uniformly grafted with macromolecules ('nanoparticle amphiphiles') robustly self-assemble into a variety of anisotropic superstructures when they are dispersed in the corresponding homopolymer matrix. Theory and simulations suggest that this self-assembly reflects a balance between the energy gain when particle cores approach and the entropy of distorting the grafted polymers. The effectively directional nature of the particle interactions is thus a many-body emergent property. Our experiments demonstrate that this approach to nanoparticle self-assembly enables considerable control for the creation of polymer nanocomposites with enhanced mechanical properties. Grafted nanoparticles are thus versatile building blocks for creating tunable and functional particle superstructures with significant practical applications.

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  1. Department of Chemical Engineering, Columbia University, New York, New York 10027, USA
  2. Department of Chemistry, Columbia University, New York, New York 10027, USA
  3. Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
  4. Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
  5. Skirball Institute for Biomolecular Medicine, New York University School of Medicine, New York 10016, USA
  6. Department of Chemical Engineering and PRISM, Princeton University, Princeton, New Jersey 08544, USA
  7. Department of Chemical Engineering, University of Texas, Austin, Texas 8712, USA
  8. Advanced Photon Source Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
  9. Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA
  10. Polymers Division, National Institutes of Standards and Technology, Gaithersburg, Maryland 20899, USA

Correspondence to: Sanat K. Kumar1 e-mail: sk2794@columbia.edu



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