title: Perturbation of the yield-stress rheology of polymer thin films by nonlinear shear ultrasound.
abstract: We investigate the nonlinear response of macromolecular thin films subjected to high-amplitude ultrasonic shear oscillation using a sphere-plane contact geometry. At a film thickness comparable to the radius of gyration, we observe the rheological properties intermediate between bulk and boundary nonlinear regimes. As the driving amplitude is increased, these films progressively exhibit oscillatory linear, microslip, and full slip regimes, which can be explained by the modified Coulomb friction law. At highest oscillation amplitudes, the interfacial adhesive failure takes place, being accompanied by a dewettinglike pattern. Moreover, the steady state sliding is investigated in thicker films with imposed shear stresses beyond the yield point. We find that applying high-amplitude shear ultrasound affects not only the yielding threshold but also the sliding velocity at a given shear load. A possible mechanism for the latter effect is discussed.
authors: LPMDI, Université Paris-Est, 5 Boulevard Descartes, 77454 Marne-la-Vallée Cedex 2, France.
authors: J
authors: J
authors: Léopoldès
authors: LPMDI, Université Paris-Est, 5 Boulevard Descartes, 77454 Marne-la-Vallée Cedex 2, France.
authors: G
authors: G
authors: Conrad
authors: Institut Langevin, ESPCI ParisTech, CNRS UMR No. 7587, 1 Rue Jussieu, 75005 Paris, France and Université Paris-Est, 5 Boulevard Descartes, 77454 Marne-la-Vallée Cedex 2, France.
authors: X
authors: X
authors: Jia