IFIS - LITORAL   24734
INSTITUTO DE FISICA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Measuring the effective viscosity of polymeric liquids under strong confinement
Autor/es:
CENCHA, LUISA G.; BERLI, CLAUDIO L. A.; RAUL URTEAGA
Lugar:
Córdoba
Reunión:
Congreso; II Brazil-Argentine Microfluidics Congress; 2019
Institución organizadora:
Universidad Nacional de Córdoba
Resumen:
The behavior of complex fluids in nanoscale confinement is currently of high interest in fundamental and applied sciences. In this work, we report an investigation of the capillary-driven flow of poly-dimethylsiloxane (PDMS) through nanoporous silicon membranes by a dynamic spectroscopy technique based on interferometry [1]. We have found that, after a slower first stage, the fluid front velocity is higher than the expected for the bulk fluid viscosity. This effect may be due to a decrease of the effective fluid viscosity, as the polymerbecomes strongly confined in the nanopore space; a result previously reported in literature for similar systems [2-4]. Nowadays it is clear that, when forced to flow through nanometer scale pores, polymeric fluids exhibit properties different from those measured in bulk flow [5], however the explanation of this fact is still one of the major concerns in the field of soft matter. In order to gain some insights about the underlying mechanisms affecting the capillary flow of polymers under confinement, we have compared our experimental results with a two fluid model, which consider a shell and a core flow having different viscosities. The analysis showed that the decrease in effective viscosity can be also understood in terms of a slippage of the polymer in the pore walls. These approaches allow one to infer some experimental responses, however further modeling with deeper insights at the nanoscale is still required.[1] Cencha, L. G., Urteaga, R. and Berli, C. L. A. Interferometric technique to determine thedynamics of polymeric fluids under strong confinement. Macromolecules 2018, 51, 21, 8721- 8728.[2] Shin, K., Obukhov, S., Chen, J.-T., Huh, J., Hwang, Y., Mok, S., Dobriyal, P., Thiyagarajan,P., Russell, T. P. Enhanced mobility of confined polymers. Nat. Mater. 2007, 6, 961.[3] Cuenca, A., Bodiguel, H. Submicron flow of polymer solutions: slippage reduction due to con-finement. Phys. Rev. Lett. 2013, 110, 108304.[4] Yao, Y., Alexandris, S., Henrich, F., Auernhammer, G., Steinhart, M., Butt, H.-J., Floudas, G.Complex dynamics of capillary imbibition of poly(ethylene oxide) melts in nanoporous alumina.J. Chem. Phys. 2017, 146, 203320.[5] Huber, P. Soft matter in hard confinement: phase transition thermodynamics, structure, tex-ture, diffusion and flow in nanoporous media. J. Phys.: Condens. Matter 2015, 27, 103102.