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

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 MatsuyamaEvans-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 morphologicaltexture diagram summarizes the magnetic field-anchoring conditions that promote anisotropic shapes. This work presents additional material processing routes to design and control biphasic morphologies in polymer-liquid crystal blend.Computed morphology phase diagram in terms of magnetic field strength L M and anchoring strength. L fQ .

Actuation of flexoelectric membranes in viscoelastic fluids with applications to outer hair cells

“…The present theory, model and computations contribute to the evolving fundamental understanding of biological shape actuation through electromechanical couplings [5][6][7][8][9][11][12][13]. Notice that the real and imaginary parts of the transfer function are the same as the average curvature moduli studied previously [18], and can be generalized for higher rheological linear models such as the well-known Jeffrey and Burgers models.…”

“…physiological actuator device whose functioning hinges on unique electromechanical properties of mesophases and that provides an example of responsive self-organized materials. The functioning of outer hair cells (OHCs) in the inner ear involves electric field-driven periodic curvature oscillations of LC elastic membranes that impart momentum and flow to the contacting viscoelastic fluids; the electric field actuation of the LC membrane is known as flexoelectricity [1][2][3][4][5][6][7][8][9][10][11][12]. The key role of OHCs is sound amplification in the presence of viscous dissipation and elastic storage [10].…”

Theoretical Platform for Liquid-Crystalline Self-Assembly of Collagen-Based Biomaterials

“…The tangential orientation minimizes the interfacial free energy at n.k = 0 where k is the interfacial normal vector. This tangential configuration, n.k = 0, emerges when the coupling coefficient,L φ−Q <0 [21,71,72,76]. The structure of the 2D tactoid is a radial helix, with tangential interface orientation at the edge and non-singular escape orientation at its center.…”

“…Simulation parameters used in this study are summarized in Table 1-also readers are referred to the Khadem and Rey [20] for detailed account of parameters selection in order to accurately capture the available experimental data. Although theL φ−Q ,L φ , and L 2 /L 1 have not been documented for tropocollagen, we choose common values which satisfy the energy transformation constraint [70][71][72]:…”

Thermodynamics of Flexible and Rigid Rod Polymer Blends

“…Under strong anchoring conditions, a magnetic field leads to a director re-orientation [148] and induces stripe domains in phase separation accompanying orientational ordering [149]. Figure 2.32 shows simulated domain pattern evolution of symmetric mixture (w 0:5) under an external field [149].…”