A Molecular Dynamics Simulation on the Self-Assembly of ABC Triblock Copolymers, 1. Effects of Block Composition in Symmetric Triblock Copolymers

Abstract

The self-assembly of ABC triblock copolymers in the microphase-separated state is investigated using an isothermal-isobaric molecular dynamics simulation. For the validation of our simulation scheme, ABA triblock copolymers are also simulated. We examine the effect of the composition (f B ) of symmetric triblock copolymers on the morphology realized in these copolymers, keeping other parameters fixed. For ABA triblock copolymers, the transition from lamellar to cylindrical morphologies is observed with increasing the composition from f B = 0.5 to f B = 0.75, and such behavior is supported by calculation results of scattering putterns. These simulated results agree well with experimental and theorotical ones, validating our simulation method. More complex structures are predicted for ABC triblock copolymers. If midblock B is the minor component, its structures are changed from lamellar, cylindrical, to spherical morphology at the interface between A/C lamellae as f B decreases. For ABC triblock copolymers with the mldblock B as the major component, the morphology of end blocks in the matrix composed of the midblock is changed from tricontinuous to spherical structures as f B increases.