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|Chremos2009.pdf||PhD thesis||10.9 MB||Adobe PDF||View/Open||My PhD thesis_RAW.zip||File not available for download||41.43 MB||Unknown|
|Title: ||Self assembly in soft matter|
|Authors: ||Chremos, Alexandros|
|Supervisor(s): ||Camp, Philip J.|
|Issue Date: ||2009|
|Publisher: ||The University of Edinburgh|
|Abstract: ||The term “soft matter” applies to a variety of physical systems, such as liquids,
colloids, polymers, foams, gels, and granular materials. The most fascinating aspect
of soft matter lies in the fact that they are not atomic or molecular in nature. They
are instead macromolecular aggregates, whose spatial extent lies in the domain 1 nm
to 1 ¹m.
Some of the most important examples of soft matter are polymers, which exhibit
intriguing and useful physical properties. In this work, the adsorption and self assembly
of linear and star polymers on smooth surfaces are studied using coarse-grained,
bead-springmolecular models and Langevin dynamics computer simulations. The
aim is to gain insight on atomic-forcemicroscopy images of polymer films on mica
surfaces, adsorbed from dilute solution following a good solvent-to-bad solvent
quenching procedure. In the case of linear polymers, under certain experimental
conditions, a bimodal cluster distribution is observed. It is demonstrated that this
type of distribution can be reproduced in the simulations, and rationalized on the
basis of the polymer structures prior to the quench. In addition to providing insight
on experimental observations, the simulation results support a number of predicted
scaling laws such as the decay of the monomer density as a function of distance from
the surface, and the scaling of the filmheight with the strength of the polymer-surface
Star polymers represent a special class of polymers, in which one end of each
linear chain is tethered to a small central core to forma single particle. The discovery
of these molecules led to the synthesis of a wide range of new materials. Their
structures are effectively considered as intermediate between those of colloids and
linear polymers. We explore the behaviour of the star polymers (which are like
“soft colloids”) in the proximity of a surface, using Langevin dynamics simulations.
A number of different measurements such as the height, radius of gyration, and
asphericity of adsorbed stars with different number of arms, are shown to provide
valuable insights on experimental findings.
The simplest soft matter systems consist of spherical, rigid colloidal particles.
Examples of such particles are chemically synthesized polystyrene or silica particles.
We investigated the neighbour distribution in a two-dimensional polydisperse harddisk
fluid, corresponding physically to a colloidal monolayer. The disk diameter
distribution was defined by a power-law with the aim of realizing a scale-free nearneighbour
network. Scale-free (power-law) behaviour is found in many important
networks, for example, in transportation systems, biochemical reactions, scientific
and movie-actor collaborations, and sexual contacts. We have provided the first
example of a scale-free network in amodel condensed-matter system.
Finally, we use genetic algorithms, a method for efficiently searching for minima
on energy landscapes, to investigate the ordered equilibrium structures formed
by binary mixtures of anisotropic dipolar particles confined on a plane, under the
presence of an external magnetic field. The anisotropy of the interparticle forces is
controlled by tilting the external magnetic field with respect to the plane. Initially, as
the field is tilted the structures are only slightly perturbed, but once the anisotropy
exceeds a critical value, completely new structures emerge.|
|Sponsor(s): ||Engineering and Physical Sciences Research Council (EPSRC)|
|Appears in Collections:||Chemistry thesis and dissertation collection|
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