Shear Induced Osmotic Pressure Determines a Reduction in Polymer Radius in Flow

Shear induced osmotic pressure has been measured and modelled for concentrated suspensions of particles. Importantly, the significance of the shear induced osmotic pressure has not been recognized in polymer rheology. The shear induced osmotic pressure results in an inward pressure on the polymer chains resulting in a shear dependent compressive force. The analytical form of the force balance equations that incorporate the effect of shear induced osmotic pressure predict a reduced polymer blob size and reducing viscosity with increasing shear rate as has been observed experimentally. Power law behavior is found for the viscosity in accord with the general behavior observed for the rheology of concentrated polymer solutions and melts.