Quasicrystals have a unique aperiodic order leading to diffraction patterns of 8-, 10-, or 12-fold rotational symmetry. They have been discovered in 1982 by Dan Shechtman. Since then they have been found in more than one hundred binary and ternary metal alloys. Beginning in 2004 there have been reports on quasicrystalline structures formed by soft colloids such as dendrimers, polymers and surfactants. This indicates that there might be general principles that favor the formation of quasicrystals, and if this would be the case, quasicrystals could be rationally designed using soft colloids with characteristic length scales up to the micron range for photonic applications.<br/><br/>We have discovered quasicrystalline phases with 12- and 18-fold rotational symmetry for soft core/shell-colloids and binary colloid mixtures in aqueous and organic solvents. Their stability range and phase transitions into FCC and BCC phases as a function of volume fraction, temperature and size have been determined by X-ray and neutron diffraction. Our studies indicate that a condition for the formation of colloidal quasicrystals is a soft repulsive interaction potential facilitating the formation of polytetrahedral particle arrangements. Using MD-simulations we have mapped the stability regions of crystalline and quasi-crystalline phases over a large range of volume fractions and core/shell size ratios. The phase diagram for the first time links previous reports of quasicrystals in nanoparticles, polymers and metal alloys as well as MD-simulations of repulsive and attractive colloid systems to provide a fundamental understanding of the structure and stability of soft quasicrystals.

Self-assembly of soft colloids into quasicrystals

2019 Fall National Meeting

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