Coarse-Grained Molecular Dynamics Study of the Interface of Polymer Blends

Abstract

A hybrid simulation of coarse-grained molecular dynamics (MD) simulation and self-consistent field (SCF) calculation has been conducted to examine the structure and strength of a polymer interface reinforced with block copolymers. We studied the interface of A-homo/AB-diblock/B-homo polymer systems, in which the B block in the copolymers was sufficiently short not to be entangled with other chains. In the coarse-grained MD simulation, the equilibrated structures in which block copolymers were concentrated at the interface were generated by our original algorithm, the density-biased Monte Carlo method. Stress-strain behavior was studied by elongating the unit cell during the coarse-grained MD simulation, and the fracture of interfaces was observed at around 4 % strain. The fracture energy was calculated by integrating the stress during elongation until the interfaces were completely separated. We found that the fracture energy was proportional to the volume fraction of block copolymer until the interface was saturated with block copolymer. The fracture energy was also proportional to the square of the length of the shorter block of the copolymer. These results were consistent with experimental results and theoretical predictions concerning the "pull-out" region, where one block of diblock copolymers was short enough not to become entangled.