Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Abstract

Superresolution microscopy unravels the nanoscale properties of densely packed stimuli-responsive polymer microgels.

Brownian dynamics of colloidal microspheres with tunable elastic properties from soft to hard

“…The melting point specified by the manufacturer is T c ∼ 25-30°C. We determine the density of α-eicosene in house to ρ wax ≃ 0.8 g/cm 3 , in agreement with literature specifications for the pure substance ρ wax = 0.79g/cm 3 [24]. Within the limited resolution of our volumetric measurements, we do not observe a significant temperature dependence of ρ wax over the range 50-10°C studied.…”

“…The remarkable features of soft particle systems, such as emulsions and microgels, can be related directly to their interfacial deformability. Since soft particles dissipate stress by compression or by deforming their interface upon shear, systems can be prepared at higher volume fractions ϕ than imposed by the random close packing limit of hard spheres ϕ rcp ≃ 0.64 [1][2][3][4][5][6]. In experiments, one can distinguish three typical cases.…”

Microgels Adsorbed at Liquid–Liquid Interfaces: A Joint Numerical and Experimental Study

“…We recall that the internal structure of microgels comprises of a rather homogeneous core, with a higher density of cross-linkers, and a loose corona complemented by a non-negligible number of dangling chains, where the number of cross-linkers is rather low. 28,29 As a consequence, a clear flattening of the corona takes place at the interface, which exposes the core, giving rise to a protrusion in the center of the microgel. A realistic modeling of the internal degrees of freedom appears to be crucial to reproduce such phenomenology.…”

“…secondly, the fact that the cross-linking density of the microgel is usually not homogeneous and decreases towards the periphery of the particle 28,29 implies that the inner core mostly retains its spherical shape also at the interface. As a result, the peculiar conformation of microgels at the liquid-liquid interface is usually referred to as a "fried-egg" shape, 30 as shown in Figure 1.…”

A new look at effective interactions between microgel particles

“…Our findings highlight that effective interactions between microgels are much more complex than usually assumed, displaying a crucial dependence on temperature and the internal core-corona architecture of the particles.Microgels are hybrid particles with a dual colloid-polymer nature, belonging to the class of so-called soft colloids [1,2]. A microgel consists of a mesoscopic cross-linked polymer network, which can deform, shrink or interpenetrate with another microgel [3,4]. Often, as a result of the synthesis conditions, a particle possesses a denser core and a more loosely crosslinked corona [5,6], which also includes so-called dangling ends [7,8].…”