Magnetic Field-Induced Shape Transitions in Multiphase Polymer-Liquid Crystal Blends

✍ Scribed by Susanta K. Das; Alejandro D. Rey

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 874 KB
• Volume: 15
• Category: Article
• ISSN: 1022-1344
• DOI: 10.1002/mats.200600024

✦ Synopsis

Abstract

Summary: This paper presents a computational study of phase separation‐phase ordering‐texturing in blends of polymer coils and rod‐like nematic liquid crystals under the presence of magnetic fields, using an extended version of the Matsuyama‐Evans‐Cates model (Phys. Rev. E 2000, 61, 2977). This work demonstrates that demixing in these blends leads to droplet morphologies with tunable droplet shapes and director textures. In contrast to filled nematics, where solids are suspended in a nematic liquid crystal matrix, demixing in coil‐mesogenic rods blends leads to nematic emulsions, in which the deformable viscoelastic polymer drops are suspended in a nematic matrix. Under strong anchoring conditions, the imposition of a magnetic field leads to a director re‐orientation that due to strong anchoring produces a droplet shape change. Magnetic field‐induced shape transitions in these blends are shown to be second order with a finite critical field threshold that diverges as anchoring strength vanishes. A morphological‐texture diagram summarizes the magnetic field‐anchoring conditions that promote anisotropic shapes. This work presents additional material processing routes to design and control bi‐phasic morphologies in polymer‐liquid crystal blend.

Computed morphology phase diagram in terms of magnetic field strength Λ~M~ and anchoring strength. Λ~ϕQ~.

magnified imageComputed morphology phase diagram in terms of magnetic field strength Λ~M~ and anchoring strength. Λ~ϕQ~.