Nanoparticle Amphiphiles
Sanat K Kumar
Department of Chemical Engineering, Columbia University, New York, NY.
Abstract
It is easy to understand the self-assembly of particles having anisotropic shapes or interactions, such as Co nanoparticles or proteins, into highly extended structures. However, there is no experimentally established strategy for creating anisotropic structures from common spherical nanoparticles. We demonstrate that spherical nanoparticles uniformly grafted with macromolecules behave akin to “nanoparticle amphiphiles” because of the dislike between the inorganic and organic constituents.1 These materials thus robustly self-assemble into a range of anisotropic superstructures under appropriate conditions of temperature and solvent quality. Theory and simulations both suggest that this self-assembly process reflects a balance between the energy gain when particle cores approach and the entropy of distorting the grafted polymers. Both liquid-state and solid-state mechanical properties are examined and their molecular bases constructed, and the role of static and dynamic scattering techniques explored.
[1] P. Akcora, H. Liu, S.K. Kumar et al, Nature Materials, 8, 354(2009)