Phase behaviors of diblock copolymer/nanorod composites under oscillatory shear flow

Abstract

AbstractThe phase behaviors of lamellar diblock copolymers (DBCPs) melts and lamellar DBCPs/nanorods (NRs) composites subjected to oscillatory shear flow, have been investigated using dissipative particle dynamics. The oscillatory shear is a quite common shearing mode used in experiments and manufacturing processes. The rich lamellar (LAM) reorientation and morphological transition of systems strongly depend on the shear amplitude and shear frequency. At very low frequency, the amplitude‐induced phase behaviors of DBCPs melts or DBCPs/NRs composites are quite similar to those subjected to a steady shear. For DBCPs/NRs case, we control NRs concentration low 15% to preserve LAM morphology in the nanocomposites, and simultaneously consider both types of selective and nonselective NRs. Our aim is to compare the different inductions on DBCPs melts or nanocomposites caused by shear amplitude and frequency, and observe how the NRs are oriented and dispersed in phase‐separated copolymers matrix while under oscillatory shear, and how the presence of selective/nonselective NRs affects the shear‐induced LAM reorientations and rheological properties of systems. Our results show the NRs orientation not only directly depend on the imposed shear flow but also is interfered by the alignment of shear‐stretched copolymer molecules. The shear viscosity decreases with the frequency decreases, also influenced by the NRs concentration and surface property. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013