Fundamental Study of Emulsions Stabilized by Soft and Rigid Particles

Abstract

Two distinct uniform hybrid particles, with similar hydrodynamic diameters and comparable zeta potentials, were prepared by copolymerizing N-isopropyl acrylamide (NIPAM) and styrene.These particles differed in their styrene to NIPAM (S/N) ratios of 1 and 8, and were referred to as S/N 1 and S/N 8. Particle S/N 1 exhibited typical behavior of soft particles, i.e., the particles shrank in bulk aqueous solutions when the temperature was increased. As a result, S/N 1 particles were interfacially active. In contrast, particle S/N 8 appeared to be rigid in response to temperature changes. In this case, the particles showed negligible interfacial activity. Interfacial shear rheology tests revealed the increased rigidity of the particle-stabilized film formed at the heptane-water interface by S/N 1 than S/N 8 particles. As a result, S/N 1 particles were shown to be better emulsion stabilizers and emulsify a larger amount of heptane compared to S/N 8 particles. The current investigation confirmed a better performance of emulsion stabilization by soft particles (S/N 1) than by rigid particles (S/N 8), reinforcing the importance of controlling softness or deformability of particles for the purpose of stabilizing emulsions.

Foaming Behavior of Polymer-Coated Colloids: The Need for Thick Liquid Films

“…Previous research confirmed that coalescence is feasible when the interfacial shear yield strength of the particle layer is exceeded. 20,27,40 In an attempt to understand why bubble coalescence was possible when the particle-laden interfaces were elastically dominant, we considered the relationship between the compressive stress acting on the thin liquid film separating two bubbles intimately in contact, 10 and the yield stress of the particle-laden interface. Assuming an average bubble diameter (2R) of 400 µm and the surface tensions ( ) taken from the data presented in Fig.…”

“…Eventually a critical strain is surpassed when the film transitions from solid-like (G' > G") to liquid-like (G' < G") response. 20,27 In an oscillation stress ramp test (data not shown) the yield point ( ) of the three particle layers, identified as the crossover in G' and G" particle spreading concentration = 0.5 wt%; spreading volume = 10 L.…”

Pickering emulsions: Preparation processes, key parameters governing their properties and potential for pharmaceutical applications

“…The way particles adsorb and arrange at the interface directly impacts the emulsion stability. Li et al [37] noticed that by varying the poly(N-isopropyl acrylamide)-styrene microgels softness, the softer ones allowed better emulsification and better stability than the rigid ones. Moreover, these microgel-stabilized emulsions can be produced using the limited coalescence principle, in the same way as rigid particle-stabilized emulsions [167].…”

Interfacial properties and emulsification performance of thylakoid membrane fragments

“…Long times for adsorption are common for complex proteins, 34 but also for soft particles that are surface active. 35,36 As indicated earlier, the thylakoid fragments as expected to consist of membrane proteins covered by lipids, which can provide a stable conformation to the protein/lipid complexes and render a soft particle that adsorbs to the interface.…”