Abstract
Using fluorescence confocal microscopy we study the adsorption of single latex microparticles at a water-water interface between demixing aqueous solutions of polymers, generally known as a water-in-water emulsion. Similar microparticles at the interface between molecular liquids have exhibited an extremely slow relaxation preventing the observation of expected equilibrium states. This phenomenon has been attributed to “long-lived” metastable states caused by significant energy barriers ΔF∼γAd≫kBT induced by high interfacial tension (γ∼10−2 N/m) and nanoscale surface defects with characteristic areas Ad≃10–30nm2. For the studied water-water interface with ultralow surface tension (γ∼10−4N/m) we are able to characterize the entire adsorption process and observe equilibrium states prescribed by a single equilibrium contact angle independent of the particle size. Notably, we observe crossovers from fast initial dynamics to slower kinetic regimes analytically predicted for large surface defects (Ad≃500 nm2). Moreover, particle trajectories reveal a position-independent damping coefficient that is unexpected given the large viscosity contrast between phases. These observations are attributed to the remarkably diffuse nature of the water-water interface and the adsorption and entanglement of polymer chains in the semidilute solutions. This work offers some first insights on the adsorption dynamics or kinetics of microparticles at water-water interfaces in biocolloidal systems.
Original language | English |
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Article number | 208003 |
Number of pages | 6 |
Journal | Physical Review Letters |
Volume | 120 |
Issue number | 20 |
DOIs | |
Publication status | Published - 15 May 2018 |