Free self-assembly of spontaneously chiral, supramolecular structures
type: CreativeWork
description: In this thesis, Molecular Dynamics simulations are used to investigate the free selfassembly of supramolecular, chiral structures. The main coarse-grained model used for this is the disc-shaped variant of the Gay-Berne potential. This is parameterised to favour face-face configurations, consistent with chromonic molecules which tend to stack due to their π − π interactions. Additionally, assemblies formed by mixtures of these discs and a second species, modelled as Lennard-Jones spheres, are investigated. Here, hot-spot zones on the rims of the discs are used to provide strong interactions with the spheres. Simulations of disc-only systems lead to self-assembly of multi-thread, chiral fibres. Depending on the choice of particle shape and face-face interaction strength, the formed fibres are reproducibly either straight or, for reasons of packing efficiency, spontaneously chiral. As they grow radially, increasing stresses cause chiral fibres to untwist either continuously or via morphological rearrangement. It is also found that, due to the kinetics of fibre initiation, the isotropic solution has to be significantly supercooled before aggregation takes place. As a result, the thermal hysteresis of the formed fibres extends to 10-20% of their formation temperatures. The kinetic barriers to the early stages of growth are investigated by the introduction of a small permanent seed. Depending on the size of the seed, monotonic fibre growth is then observed 5-10% above the normal formation temperatures. On introducing Lennard-Jones spheres and hot-spot zones at the rims of discs, twisted bilayer ribbons, sandwiching a helicoidal sphere layer, are obtained. Systematic investigation of the effects of hot-spot size on the formation and structural properties of these twisted bilayers is then performed. This shows that lateral growth of these bilayers, and the associated increases in bend stresses, lead to the development of defect lines. For relatively small hot-spot sizes, ro…
abstract: In this thesis, Molecular Dynamics simulations are used to investigate the free selfassembly of supramolecular, chiral structures. The main coarse-grained model used for this is the disc-shaped variant of the Gay-Berne potential. This is parameterised to favour face-face configurations, consistent with chromonic molecules which tend to stack due to their π − π interactions. Additionally, assemblies formed by mixtures of these discs and a second species, modelled as Lennard-Jones spheres, are investigated. Here, hot-spot zones on the rims of the discs are used to provide strong interactions with the spheres. Simulations of disc-only systems lead to self-assembly of multi-thread, chiral fibres. Depending on the choice of particle shape and face-face interaction strength, the formed fibres are reproducibly either straight or, for reasons of packing efficiency, spontaneously chiral. As they grow radially, increasing stresses cause chiral fibres to untwist either continuously or via morphological rearrangement. It is also found that, due to the kinetics of fibre initiation, the isotropic solution has to be significantly supercooled before aggregation takes place. As a result, the thermal hysteresis of the formed fibres extends to 10-20% of their formation temperatures. The kinetic barriers to the early stages of growth are investigated by the introduction of a small permanent seed. Depending on the size of the seed, monotonic fibre growth is then observed 5-10% above the normal formation temperatures. On introducing Lennard-Jones spheres and hot-spot zones at the rims of discs, twisted bilayer ribbons, sandwiching a helicoidal sphere layer, are obtained. Systematic investigation of the effects of hot-spot size on the formation and structural properties of these twisted bilayers is then performed. This shows that lateral growth of these bilayers, and the associated increases in bend stresses, lead to the development of defect lines. For relatively small hot-spot sizes, ro…
author: Dastan, Alireza
language: en
date published: 2017-10
date modified: 2026-07-24T06:31:09Z
provider: Sheffield Hallam University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Sheffield Hallam University

PropertyValue
property ID: DOI
value: 10.7190/shu-thesis-00044