Diblock-copolymer thin films under shear.
The behavior of lamellae forming diblock-copolymer melts confined by two non-selective substrates under shear is studied by means of molecular dynamics simulations. Since the substrate/copolymer preferential interaction is absent, the vertically oriented lamellae (L⊥) are formed. The response of L⊥phase under transverse and perpendicular modes of shear is studied for a wide range of shear rates, γ̇. In particular, shear deformation and reorientation transition, flow behavior, and difference in the macroscopic response under the two modes of shear are discussed. We show that an inclined lamellae state observed for transverse shear below a critical shear rate γ̇*is stabilized by a cyclic motion of chains close to the substrates. The value of γ̇*, at which lamellae dissolve and reorient along the flow field during transverse shear, coincides with the onset of shear-thinning. For γ̇<γ̇*, the shear viscosity for transverse shear is much larger compared to that observed in perpendicular shear, while there is no difference for γ̇>γ̇*.
Department of Physics, National Institute of Technology, Manipur, Imphal 795004, India.
Lenin S
LS
Shagolsem
Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany.
Torsten
T
Kreer
Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany.
Andre
A
Galuschko
Leibniz Institute of Polymer Research Dresden, 01069 Dresden, Germany.
Jens-Uwe
JU
Sommer