Microphase transitions of block copolymer/homopolymer under shear flow

Abstract

Cell dynamics simulation is used to investigate the phase behavior of block copolymer/homopolymer mixture subjected to a steady shear flow. Phase transitions occur from transverse to parallel and then to perpendicular lamellar structure with an increase of shear rate and this is the result of interaction between the shear flow and the concentration fluctuation. Rheological properties, such as normal stress differences and shear viscosity, are all closely related with the direction of the lamellae. Furthermore, we specifically explore the phase behavior and the order parameter under weak and strong shear of two different initial states, and realize the importance of the thermal history. It is necessary to apply the shear field at the appropriate time if we want to get what we want. These results provide an easy method to create ordered, defect-free materials in experiment and engineering technology through imposing shear flow.

Is the “Bricks-and-Mortar” Mesophase Bicontinuous? Dynamic Simulations of Miktoarm Block Copolymer/Homopolymer Blends

“…For all cases studied here, the application of shear results in a transition from the bicontinuous phase to one with discrete A domains where the only direction of percolation is along the sheared direction. This phenomenon fits into a broader category of shear-induced morphology transitions that have been observed in other systems, including blends of the block copolymer and homopolymer. , The cluster analysis on the postsheared configurations confirms that the A domains are more discontinuous than in the equilibrium configurations (this behavior appears for any shear rate studied that stabilizes a flow). This is no surprise for the aligned cylindrical morphologies, where the shear has aligned them and annealed defects out such that discrete cylinders are now hexagonally packed.…”

Pattern formation mechanisms in sphere-forming diblock copolymer thin films

“…In recent years, such models have been used to study a variety of systems under different conditions, including shear and other external fields, curvature and patterned substrates, and pattern formation in 3D [20,33,[36][37][38][39][40]. In this work, the free energy parameters were selected to capture the desired symmetry and segregation strength of the block copolymer hexagonal phase [20,34,35].…”

Numerical investigation of local defectiveness control of diblock copolymer patterns

“…Therefore, it is very important to control the local defects of self-assembled polymer patterns with the application of these materials. As the efforts to rectify this, many researches and techniques such as electric fields [20], flow [21], shear application [22][23][24], thermal treatment [25], chemically pre-patterned surface (chemoepitaxy) [26,27], and topographical confinement (graphoepitaxy) [28] have been carried out to reduce the defect density in specific pattern-forming block copolymer thin films. Among the controlling method, authors in [19] proposed an appropriate substrate design and achieved a defect-free pattern formation.…”