Effect of nanoconfinement on liquid-crystal polymer chains

Abstract

We apply a Monte Carlo polymerization model for Gay-Berne monomers that we have recently introduced [J. Chem. Phys. 121, 9123 (2004)] to investigate with computer simulations the effects of nanoconfinement and anchoring type on the structure of the main chain liquid-crystal polymers formed in thin films, in the presence of several types of surface alignment: parallel to the interface (random and uniform) or perpendicular to it (homeotropic).We perform first a study of the confined monomers and then we examine the features of the polymer chains obtained from an isotropic or nematic sample. We find a significant effect of the anchoring conditions on the characteristics of the chains and particularly striking differences between planar and homeotropic boundaries. Furthermore, our results indicate that the choice of different anchorings could be used to tune the linearity and degree of polymerization of the chains.

Molecular simulations elucidate electric field actuation in swollen liquid crystal elastomers

“…The preferred bond directions are parallel to the long and short ellipsoid axes for bond sites at ellipsoid ends and on the equator, respectively. For compatibility with previous research, we here take s e ¼ 0.15σ s , δs m ¼ 0.25σ s , and k s ¼ 500ϵ∕σ 2 s ≈ 2.76 N∕m for stretching, and θ e ¼ 0°, δθ m ¼ 150°, and k θ ¼ 3.8 × 10 −4 ϵ∕deg 2 ≈ 1.72 × 10 −21 J∕rad 2 for bending (21,42,43).…”

“…The deviation from its equilibrium value θ e is given by δθ ij ¼ jθ ij − θ e j, with a limitation that δθ ij < δθ m . Then, the FENE bond energy can be written as (42,43) …”

A scale-bridging modeling approach for anisotropic organic molecules at patterned semiconductor surfaces

“…In the literature (see, e.g. [45][46][47]) several expressions for the interaction between a GB-like particle and a planar substrate have been proposed and used for simulations of, e.g., GB bulk fluids in contact with a wall [48] or confined GB films [49]. Here we use a simpler expression which is motivated by two important results from DFT calculations [20]: First, the energetically most favourable distance between the molecule's center of mass and the surface is given by z min ≈ 0.35 nm, which corresponds approximately to the diameter d of our GB-particles (see Table I).…”

Capillary Nematization of Semiflexible Polymers

“…In the context of such applications, the interaction of the semiflexible macromolecules with confining walls clearly is of great importance. Thus, the effect of confining walls on the semiflexible polymers in solutions and melts has been studied theoretically by various computational and analytical approaches . However, this work suffers from certain limitations.…”

“…Thus, the effect of confining walls on the semiflexible polymers in solutions and melts has been studied theoretically by various computational and analytical approaches. [10][11][12][13][14][15][16][17][18][19][20] However, this work suffers from certain limitations. For example, analytical theories based on self-consistent field theory (SCFT) extended to wormlike polymers [13,14,18,19] treat excluded-volume effects among effective monomers only on a simplified mean-field-type level and do not account for the packing effects of the monomeric units near repulsive walls.…”