Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Crystallization, Nucleation and Self Assembly I (joint session CPP, DY)
CPP 6.6: Vortrag
Montag, 16. März 2015, 11:00–11:15, PC 203
Crystallization of binary colloidal mixtures with polymer-induced attraction — •Nicole Schaertl1, 2, Thomas Palberg3, and Eckhard Bartsch1, 2 — 1Institut für Physikalische Chemie, Universität Freiburg, Deutschland — 2Institut für Makromolekulare Chemie, Universität Freiburg, Deutschland — 3Institut für Physik, Universität Mainz, Deutschland
Polystyrene (PS) microgel colloids serve as model system for hard spheres (HS). Binary mixtures of dispersed small (S) and large (L) PS particles with diameter ratios of S to L close to a value of Γ = 0.8 have been widely used to investigate glass formation as well as re-entrant melting introduced by short-ranged depletion attraction. Previously, we have shown that depletion attractions not only enhance particle mobility, leading to a melting of the glass, but also enforce crystallization of a colloidal eutectic which is kinetically suppressed in the corresponding HS system [1]. Here we show that a subtle change of the system parameters to slightly larger Γ leads to a completely different enforced crystallization scenario. Using static light scattering to investigate structure and kinetics including crystal size growth and packing, we observe hexagonal superlattices instead of single-component crystals. Our findings can be rationalized by the occurrence of stable binary crystals LS2, so-called Laves phases, in agreement with computer simulations by Hynninen et al. [2].
[1] Kozina et al., Soft Matter 10, 9523 (2014) [2] Hynninen et al., J. Chem. Phys. 131, 064902 (2009)