Nanorings in planar confinement: the role of repulsive surfaces on the formation of lacuna smectics
File(s)
Published version
Author(s)
Avendano, Carlos
Jackson, G
Wensink, Henricus H
Type
Journal Article
Abstract
We study the structure and liquid-crystalline phase behaviour of a model of nonconvex
circular soft-repulsive nanorings con ned in a planar slit geometry using
molecular-dynamics simulation. The separation distance between the structureless
parallel soft-repulsive walls is large enough to allow for the formation of a distinct
bulk phase in the central region of the box which is in coexistence with the adsorbed
uid thus allowing the analysis of single wall e ects. As the concentration
of the particles is increased, the
uid adsorbs (wets) onto the planar surfaces leading
to the formation of well-de ned smectic-A layers with a spacing proportional to
the diameter of the rings. An analysis of the nematic order parameter at distances
perpendicular to the surface reveals that the particles in each layer exhibit antinematic
behaviour and planar (edge-on) anchoring relative to the short symmetry
axis of the rings. This behaviour is in stark contrast to the behaviour observed in
convex disc-like particles that have the tendency to form nematic (discotic) structures
with hometropic (face-on) anchoring. The smectic phases formed by nanorings
in the bulk and under con nement are characterized by the formation of low-density
layered liquid-crystalline states with large voids, referred to here as lacuna smectic
phases. In contrast to what is typically found for con ned liquid-crystalline systems
involving convex particles, no apparent biaxiality is found for the nanorings in planar
con nement. We argue that formation of the low-density lacuna smectic layers with
planar anchoring is a consequence of the non-convex shape of the circular rings that
allow for interpenetration between the particles as observed for nanorings under
bulk conditions [Avenda~no et al., Proc. Natl. Acad. Sci. U. S. A. 113, 9699 (2016);
H. H. Wensink and C. Avenda~no, Phys. Rev. E 94 062704 (2016)].
circular soft-repulsive nanorings con ned in a planar slit geometry using
molecular-dynamics simulation. The separation distance between the structureless
parallel soft-repulsive walls is large enough to allow for the formation of a distinct
bulk phase in the central region of the box which is in coexistence with the adsorbed
uid thus allowing the analysis of single wall e ects. As the concentration
of the particles is increased, the
uid adsorbs (wets) onto the planar surfaces leading
to the formation of well-de ned smectic-A layers with a spacing proportional to
the diameter of the rings. An analysis of the nematic order parameter at distances
perpendicular to the surface reveals that the particles in each layer exhibit antinematic
behaviour and planar (edge-on) anchoring relative to the short symmetry
axis of the rings. This behaviour is in stark contrast to the behaviour observed in
convex disc-like particles that have the tendency to form nematic (discotic) structures
with hometropic (face-on) anchoring. The smectic phases formed by nanorings
in the bulk and under con nement are characterized by the formation of low-density
layered liquid-crystalline states with large voids, referred to here as lacuna smectic
phases. In contrast to what is typically found for con ned liquid-crystalline systems
involving convex particles, no apparent biaxiality is found for the nanorings in planar
con nement. We argue that formation of the low-density lacuna smectic layers with
planar anchoring is a consequence of the non-convex shape of the circular rings that
allow for interpenetration between the particles as observed for nanorings under
bulk conditions [Avenda~no et al., Proc. Natl. Acad. Sci. U. S. A. 113, 9699 (2016);
H. H. Wensink and C. Avenda~no, Phys. Rev. E 94 062704 (2016)].
Date Issued
2018-07-05
Date Acceptance
2018-05-11
Citation
Molecular Physics, 2018, 116 (21-22), pp.2901-2910
ISSN
0026-8976
Publisher
Taylor & Francis
Start Page
2901
End Page
2910
Journal / Book Title
Molecular Physics
Volume
116
Issue
21-22
Copyright Statement
© 2018 Taylor & Francis. This is an Accepted Manuscript of an article published by Taylor & Francis in Molecular Physics on 05 July 2018, available online: https://doi.org/10.1080/00268976.2018.1484950
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.tandfonline.com/doi/full/10.1080/00268976.2018.1484950
Grant Number
EP/E016340/1
EP/J014958/1
Subjects
Science & Technology
Physical Sciences
Chemistry, Physical
Physics, Atomic, Molecular & Chemical
Chemistry
Physics
Lacuna smectics
surface ordering
liquid crystals
non-convex ring-like particles
molecular dynamics
INTERFACIAL FREE-ENERGY
ONSAGER TRIAL-FUNCTION
EQUATION-OF-STATE
LIQUID-CRYSTALS
PHASE-BEHAVIOR
HARD SPHEROCYLINDERS
MOLECULAR-DYNAMICS
MONTE-CARLO
COLLOIDAL NANOCRYSTALS
PARTICLES
0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics
0306 Physical Chemistry (incl. Structural)
0307 Theoretical and Computational Chemistry
Chemical Physics
Publication Status
Published
Date Publish Online
2018-07-05