Unique self-assembly behaviors of ABCA tetrablock copolymer*

The self-assembly behavior of linear ABCA tetrablock copolymers is investigated using self-consistent field theory (SCFT). Although the general mechanism of block copolymer self-assembly has been well established, the self-assembly behaviors of some block copolymers are still hard to be understood and are even quite counterintuitive. Here we focus on the self-assembly of symmetric ABCA linear tetrablock copolymer. Our results indicate that the Janus-like superspherical phase can exist stably when the Flory-Huggins interaction between B and C blocks is much larger than the other two interactions. Moreover, a helical-Janus spherical phase is predicted to compete with the Janus phase. Meanwhile, the Janus-like supercylinder is predicted to be only metastable, and instead supercylinders composed of B/C-helices and B/C-stacked-disks are predicted to be stable. The stability of these novel structures is mainly dictated by the competition between the stretching energy and interfacial energy.