Branched colloidal inorganic nanoparticles are currently emerging as promising functional materials due to their potential applications in optics and electronics and as building blocks for superlattices.1,2 In contrast, the controlled preparation of branched structures based on soft matter systems remains much less developed, despite the recent discoveries of �Y� junctions and some more highly branched morphologies in surfactant- or block copolymer-based micelles.3,4 Herein, we report the formation of multi-armed and branched micelles through crystallization-driven self-assembly of block copolymers containing a core-forming poly(ferrocenyldimethylsilane) (PFDMS) block. Multi-armed micelles were prepared by the growth of cylindrical micelles on the nanocrystals of PFDMS homopolymer (Figure 1a).5 The resulting multi-armed micelles possessed hierarchical multipod structures with monodisperse and tunable arm lengths. The termini of the arms remained active to the addition of further block copolymer unimers and multi-armed block co-micelles with segmented arm chemistries and variable segment sequences were prepared. Coronal crosslinking followed by nanocrystal dissolution also led to the release of non-centrosymmetric AB cylindrical diblock co-micelles.6 On the other hand, the branched micelles were prepared by the growth of thinner-core cylindrical micelles at the termini of the thicker-core cylindrical micelle seeds (Figure 1b).7 The branched micelles possessed structures with monodisperse middle segments and, in most cases, two branches at the seed terminus. After crosslinking of the coronas, the branched micelles become resistant to dissolution in good solvents for both blocks and can be manipulated as colloidally-stable nanomaterials. Figure 1. Schematic representations of (a) multi-armed and (b) branched micelles.References Manna, L.; Milliron, D. J.; Meisel, A.; Scher, E. C; Alivisatos, A. P. Nat. Mater. 2003, 2, 382-385.Milliron, D. J.; Hughes, S. M.; Cui, Y.; Manna, L.; Li, J.; Wang, L.-W.; Alivisatos, A. P. Nature 2004, 430, 190-195.Li, Z.; Kesselman, E.; Talmon, Y.; Hillmyer, M. A.; Lodge, T. P. Science 2004, 306, 98-101.Cui, H.; Chen, Z.; Zhong, S.; Wooley, K. L.; Pochan, D. J. Science 2007, 317, 647-650.Qiu, H.; Cambridge, G.; Winnik, M. A.; Manners, I. J. Am. Chem. Soc. 2013, 135, 12180-12183.Rupar, P. A.; Chabanne, L.; Winnik, M. A.; Manners, I. Science 2012, 337, 559-562.Qiu, H.; Du, V. A.; Winnik, M. A.; Manners, I. J. Am. Chem. Soc. 2013, 135, 17739-17742.

Multi-armed and branched micelles via crystallization-driven self-assembly

248th National Meeting (2014)

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