Domain patterns in a diblock copolymer-diblock copolymer mixture with oscillatory particles

Abstract

We investigate the orientational order transition of striped patterns in microphase structures of diblock copolymer-diblock copolymer mixtures in the presence of periodic oscillatory particles. Under certain conditions, although the macrophase separation of a system is almost isotropic, microphase separation of one diblock copolymer takes place and becomes anisotropic gradually. By changing the oscillatory frequency and amplitude, the orientational order transition of a striped microphase structure from the state parallel to the oscillatory direction to the state perpendicular to the oscillatory direction is observed. We also find that the order transition occurs when we change the initial composition ratio. Furthermore, we examine the domain size and the orientational order parameter of microstructure in the process of orientational order transition. The results may provide guidance for experimentalists. This model system can also give a simple way to realize orientational order transition of soft materials by changing the oscillatory field.

Phase behaviors in a binary mixture of diblock copolymers confined between two parallel walls

“…and ξ = φ C − φ D as the independent variables, which are similar to our previous work. [22,36] These three quantities are the order parameters to describe the phase behavior of the system. Among them, ψ reflects the segregation of binary mixture, whereas φ and ξ are the local concentration differences between monomers A and B and between monomers C and D, respectively.…”

“…here, d 1 , d 2 , and d 3 terms correspond to the surface tensions, and the last term on the right is the surface field of the wallblock interaction. [79] Furthermore, we use η = ψ − ψ c instead of ψ, [18,21,22,34,80,81] where ψ c is the volume fraction at the critical point of the macrophase separation of two different copolymers. It is obtained as…”

“…When the binary mixture of AB diblock copolymer and CD diblock copolymer is asymmetric, the minority CD diblock copolymer will form islands in the majority AB diblock copolymer, and this has already been proved by our previous works. [18,22] Furthermore, the incompatibility and the short-range interactions of different monomers causes differ-ent block copolymers to form micro-level striped structures (Fig. 1(a)).…”

“…Applied external fields are promising candidates to achieve that goal. [19] Such fields can be an electric field, [20][21][22][23][24][25][26] shear flow, [27][28][29][30][31] and surface fields. [32][33][34][35][36][37][38] By using self-consistent field theory, Matsen has examined the undulation mode in films of parallel lamellae and calculated the critical electric field, beyond which the mode becomes unstable.…”

“…[20] Recently, our group has also investigated the orientational order transition of striped patterns in microphase structures of diblock copolymer-diblock copolymer mixtures in the presence of periodic oscillatory particles. [22] Moreover, Morozov and coworkers have produced many works about the shear-induced phase transi-tions in polymer mixtures. [28][29][30] Surface fields are, in particular, prominent in confined geometries, such as parallel wall confinement, [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] nano-cylinder tube confinement, [57][58][59][60][61][62][63][64][65][66][67][68][69][70] and spherical confinement.…”