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    Anisotropic Self-Assembly from Isotropic Colloidal Building Blocks

    Year: 2017

    Journal: J. Am. Chem. Soc., Volume 139, DEC 6, page 17464–17473

    Authors: Rey, Marcel; Law, Adam D.; Buzza, D. Martin A.; Vogel, Nicolas

    Organizations: Deutsche Forschungsgemeinschaft (DFG) [VO 1824/6-1]; Interdisciplinary Center for Functional Particle Systems (FPS)

    Spherical colloidal particles generally self-assemble into hexagonal lattices in two dimensions. However, more complex, non-hexagonal phases have been predicted theoretically for isotropic particles with a soft repulsive shoulder but have not been experimentally realized. We study the phase behavior of microspheres in the presence of poly(N-isopropylacrylamide) (PNiPAm) microgels at the air/water interface. We observe a complex phase diagram, including phases with chain and square arrangements, which exclusively form in the presence of the microgels. Our experimental data suggests that the microgels form a corona around the microspheres and induce a soft repulsive shoulder that governs the self-assembly in this system. The observed structures are fully reproduced by both minimum energy calculations and finite temperature Monte Carlo simulations of hard core-soft shoulder particles with experimentally realistic interaction parameters. Our results demonstrate how complex, anisotropic assembly patterns can be realized from entirely isotropic building blocks by control of the interaction potential.
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