(738a) Molecular Simulation Study of Self-Assembly of Tethered V-Shaped Nanoparticles

The desire to fabricate nanostructured materials in a controllable manner has consistently motivated the search for effective assembly techniques. Bottom-up approaches such as self-assembly, as opposed to conventional top-down methods, offer the potential means to arrange large numbers of structural units, or building blocks, into multidimensional ordered structures. Recently, computer simulation has shown how nanostructures can be built via self-assembly by functionalizing nanoparticles with polymer tethers.[1] Combined with the ability to attach tethers to specific points on the surface of nanoparticles, the diversity of synthesized nanoparticle shapes forms an impressive collection of exotic nano-building blocks for assembly.[2] Here we investigate the self-assembly of polymer-tethered V-shaped nanoparticles.[3] These building blocks have many similarities with so-called ?bent-core? or ?banana? molecules, which exhibit a variety of novel liquid crystalline phases, or ?B? phases.[4, 5] Among the most interesting characteristics in these B phases are switching polar ordering and spontaneous chirality. If these phase behaviors could be reproduced at larger than currently demonstrated (i.e. molecular) length scales, for instance, at visible wavelengths, novel optical and electronic applications including photonic band gap and negative refraction index materials (NIMs) can be made feasible. To achieve this goal, it is instructive to compare the phase behavior of bent-core molecules with that of their mesoscopic analog, tethered V-shaped nanoparticles. We further compare our simulation results with those of polymer-tethered nanorods[6-8], a limit of tethered V-shaped nanoparticles in which the opening angle is 180 degrees. We show how the V-shaped geometry alters the phase diagram of tethered nanorods, and how the immiscibility between particles and tethers leads to structures not previously predicted for bent-core molecules.

References

[1] Z. Zhang, M. A. Horsch, M. H. Lamm, S. C. Glotzer, Nano Letters 2003, 3.

[2] S. C. Glotzer, M. J. Solomon, Nature Materials 2007, 6.

[3] T. D. Nguyen, Z. Zhang, S. C. Glotzer, preprint.

[4] R. A. Reddy, C. Tschierske, Journal of Materials Chemistry 2006, 16, 907.

[5] C. Keith, C. Tschierske, Chemistry-A European Journal 2007, 13, 2556.

[6] M. A. Horsch, Z. Zhang, S. C. Glotzer, Physical Review Letters 2005, 95.

[7] M. A. Horsch, Z. Zhang, S. C. Glotzer, Nano Letters 2006, 6.

[8] M. A. Horsch, Z. Zhang, S. C. Glotzer, Journal of Chemical Physics 2006, 125.