Premium
Structural Changes in Block Copolymer Solutions under Shear Flow as Determined by Non‐Equilibrium Molecular Dynamics
Author(s) -
Rychkov Igor,
Yoshikawa Kenichi
Publication year - 2004
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/mats.200300018
Subject(s) - gyroid , lamellar structure , shear rate , shear (geology) , shear flow , copolymer , materials science , anisotropy , lamellar phase , molecular dynamics , phase transition , perpendicular , simple shear , thermodynamics , rheology , polymer , chemistry , composite material , geometry , optics , physics , computational chemistry , mathematics
Summary: A non‐equilibrium molecular dynamics computer simulation on microsegregated solutions of symmetrical diblock copolymers is reported. As the polymer concentration increases, the system undergoes phase transitions in the following order: body centered cubic (BCC) micelles, hexagonal (HEX) cylinders, gyroid (GYR) bicontinuous networks and lamellae (L), which are the same morphology reported for block copolymer melts. Structural classification is based on the patterns of the anisotropic static structure factor and characteristic 3‐dimensional images. The systems in the BCC micellar ( ρσ 3 = 0.3) and HEX cylindrical ( ρσ 3 = 0.4) phases were then subjected to a steady planar shear flow. In weak shear flow, the segregated domains in both systems tend to rearrange into sliding parallel close‐packed layers with their normal in the direction of the shear gradient. At higher shear rates, both systems adopt a perpendicular lamellar structure with the normal along the neutral direction. A further increase in the shear rate results in a decrease in lamellar spacing without any further structural transitions. Two critical shear rate values that correspond to the demarcation of different structural behaviors were found.Shear‐induced BCC‐LAM phase transition.