Rheology and morphology of no-slip sheared polymer nanocomposite under creep condition

Dissipative particle dynamics simulations are performed on wet polymer nanocomposite blends under the discrete imposed velocity profile and no-slip boundary conditions. To be able to study the chain length dependency of the rheological properties, a number of blends of mono-disperse polymer chains of lengths varying from 10 to 100 repeat units and nanoparticles of diameters 2.5 and 5 have been simulated. The wall velocity was imposed on a thin polymer layer (the no-slip layer). Linear velocity profiles for polymer confined in the pore were observed at the steady state. We found that the flow has a shear thinning effect on the chains with a radius of gyration less than the filler radius. Long chains (with a radius of gyration longer than the filler's radius), however, obey the Newtonian behavior over a much wider shear rate than that which causes shear thinning in short chains. The effect of particle-monomer interactions, polymer entanglements, chain morphology, and link formation on the shear rate dependency of the viscosity coefficient has been studied. Our results show that the particle-polymer interactions have no effect on shear thinning behavior of the blend. In contrast, the long range polymer-polymer interactions and the chain length have considerable effects on the rheological behavior of the blend. Finally, the phase diagram of the rheological properties of polymer nanocomposite as a function of strain rate and the chain length is extracted.