Anomalous Viscosity Reduction and Hydrodynamic Interactions of Polymeric Nanocolloids in Polymers

Abstract

One of the central dogma of fluid physics is the no-slip boundary condition whose validity has come under scrutiny, especially in the fields of micro and nanofluidics.Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective viscosity experienced by polymeric nano colloids moving through a highly viscous and confined polymer, well above its glass transition temperature. The extent of reduction in effective interface viscosity increases with decreasing temperature and polymer film thickness. Concomitant with the reduction in effective viscosity we also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these colloids with an anomalous power law * To whom correspondence should be addressed † Indian Institute of Science ‡ Albert-Ludwig-University of Freiburg ¶ Deutsches Elektronen Synchrotron DESY 1 exponent of ∼ 2 at the lowest temperatures and film thickness studied. Such strong hydrodynamic interactions are not expected for polymeric colloidal motion in polymer melts. We suggest hydrodynamics, especially slip present at the colloid-polymer interface which determines the observed reduction in interface viscosity and presence of strong hydrodynamic interactions.

Nanoparticle–polymer interfacial layer properties tune fragility and dynamic heterogeneity of athermal polymer nanocomposite films

“…3(c)) based mixtures, it can be observed that the η of PNCs with smaller f is comparably lower than the neat polymers, while the samples with higher f show a slight increase in η. Such reduction in the viscosity of PNC was observed earlier [7,[44][45][46] and alluded to the presence of thin interface layer surrounding the nanoparticles with reduced surface viscosity [7,44] Our earlier observations [31] also indicated the presence of an IL with reduced viscosity compared to the bulk. To quantify the temperature dependence of the observed viscosity, we have modeled the viscosity plots with VFT equation as given in eqn.…”

Rheo-XPCS

“…8. Another very recent XPCS study by Begam et al on nanoparticle motion in thin polymer films observed greatly enhanced particle mobility, which the authors attributed to strong hydrodynamic interactions and slip at the particle-polymer interface [48].…”

Adsorption-induced slip inhibition for polymer melts on ideal substrates

“…In the past few decades, there have been many experiments measuring deviations from the no-slip boundary condition at microscopic length scales [1][2][3][4][5]. These measurements have stimulated the interest in hydrodynamic slip for both the fundamental understanding of the molecular mechanisms involved, as well as the impact of slip on technological applications [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”