Disperse cyclic diblock copolymer: another promising candidate for fabricating irregular bicontinuous structure

Abstract

In this work, dissipative particle dynamics simulations are carried out to investigate the phase behaviour of cyclic c-AB diblock copolymers with different designed dispersities in molecular weight distribution. Phase diagrams are constructed and detailed comparisons are carried out for monodisperse, one-component and two components disperse systems. For monodisperse system, our simulation results show a good agreement with self-consistent field theory. For one-component disperse system, the symmetry of the phase diagram centred at is found broken and the order–order transition boundaries are shifted towards larger volume fraction of disperse component. We also find that in one-component disperse c-AB system, an irregular bicontinuous (BIC) structure can be formed by monodisperse minority component in a 10% wide composition window where the majority component is disperse. Results are also compared with those of linear l-AB diblock and l-ABA triblock copolymers. Very similar to l-ABA system, both A and B blocks in two-components disperse c-AB system can form BIC structure, each of them occupies 10% wide composition window that flanks the lamellar window in the phase diagram. Further analyses show that for a given chain length, A blocks in cyclic c-AB system will form BIC structure at larger volume fraction of A block and therefore such BIC structure will have thicker internal network pipes than that in linear triblock l-ABA system. Consequently, BIC structure formed by c-AB diblock copolymer will have a larger specific surface area than that formed by l-ABA triblock copolymer. These results indicate that disperse c-AB diblock copolymer can be another promising candidate for fabricating irregular bicontinuous structure for better material performances.