Colloidal particle adsorption at water/water interfaces with ultra-low interfacial tension
| Autor: | Keal, Louis, Colosqui, Carlos E., Tromp, Hans, Monteux, Cecile |
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| Rok vydání: | 2017 |
| Předmět: | |
| Zdroj: | Phys. Rev. Lett. 120, 208003 (2018) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevLett.120.208003 |
| Popis: | Using fluorescence 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 $\Delta{\cal F}\sim \gamma A_d\gg k_B T$ induced by high interfacial tension ($\gamma \sim 10^{-2}$ N/m) and nanoscale surface defects with characteristic areas $A_d \simeq$ 10--30 nm$^2$. For the studied water/water interface with ultra-low surface tension ($\gamma \sim 10^{-4}$ N/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 ($A_d \simeq$ 500 nm$^2$). 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/kinetics of microparticles at water/water interfaces in bio-colloidal systems. Comment: Supplemental Material includes analysis of damping coefficients and experimental measurements of polymer adsorption on latex particles |
| Databáze: | arXiv |
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