2001/08/24 by Sandra Barsky, Mark O. Robbins · 1 citation
Chemical Engineering · Materials Science · Physics and Astronomy · #Block Copolymer Self-Assembly #Material Dynamics and Properties #Rheology and Fluid Dynamics Studies #cond-mat.mtrl-sci #cond-mat.soft
paper · pdf · doi:10.1103/physreve.65.021808
8 pages, 8 figures
arxiv created 2001/08/24 · openalex publication_date 2002/01/25 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Nonequilibrium molecular-dynamics simulations are used to study the shear-thinning behavior of immiscible symmetric polymer blends. The phase-separated polymers are subjected to a simple shear flow imposed by moving a wall parallel to the fluid-fluid interface. The viscosity begins to shear thin at much lower rates in the bulk than at the interface. The entire shear-rate dependence of the interfacial viscosity is consistent with a shorter effective chain length s(*) that also describes the width of the interface. This s(*) is independent of chain length N and is a function only of the degree of immiscibility of the two polymers. Changes in polymer conformation are studied as a function of position and shear rate. Shear thinning correlates more closely with a decrease in the component of the radius of gyration along the velocity gradient than with elongation along the flow. At the interface, this contraction of chains is independent of N and consistent with the bulk behavior for chains of length s(*). The distribution of conformational changes along chains is also studied. Central regions begin to stretch at a shear rate that decreases with increasing N, while shear induced changes at the ends of chains are independent of N.