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Deformable particles with anisotropic interactions: unusual field-induced structural transitions in ultrasoft ionic microgel colloids
Mohanty, Priti S.
Division of Physical Chemistry, Lund University, Lund, Sweden - Department of Chemistry, University of Fribourg, Fribourg, Switzerland
Department of Physics and Physical Oceanography, Memorial University, St. John's, Canada
Division of Physical Chemistry, Lund University, Lund, Sweden
- Soft MatterSoft Matter. - 2012, vol. 8, no. 42, p. 10819-10822
Ionic microgels are intriguing soft and deformable colloids with an effective pair potential that crosses over from Yukawa-like at large distances to a much softer repulsive interaction at short distances. Here we report the effect of adding an anisotropic dipolar contribution to colloids with such “ultra-soft” interactions. We use an alternating electric field to induce a tunable dipolar contribution, and study the resulting particle self-assembly and phase transitions in situ with confocal laser scanning microscopy. We find significant field-induced structural transitions at low as well as at very high effective volume fractions. At ϕeff = 0.1 we observe a transition from an isotropic to a string fluid. At ϕeff = 0.85, there is a reversible transition from an amorphous to a dipolar crystalline state, followed by the onset of a gas–(string) solid coexistence. At ϕeff = 1.6 and 2.0, i.e. far above close packing, evidence for a field-induced arrested phase separation is found.
- Faculté des sciences et de médecine
- Département de Chimie
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