Microphase transitions of block copolymer/homopolymer under shear flow

TL;DR

This study uses cell dynamics simulation to explore how shear flow influences phase transitions and rheological properties in block copolymer/homopolymer mixtures, revealing the importance of shear timing and thermal history.

Contribution

It demonstrates the phase transition sequence under shear flow and highlights the role of thermal history in controlling material structure and properties.

Findings

Phase transitions from transverse to parallel and perpendicular lamellae with increasing shear rate.

Rheological properties are closely related to lamellae orientation.

Shear timing and thermal history significantly affect phase behavior.

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.