Self-Assembly, Elasticity, and Orientational Order in Soft Matter

Bibliographic Details
Main Author:	Geng, Jun
Language:	English
Published:	Kent State University / OhioLINK 2012
Subjects:	Condensed Matter Physics Physics Liquid Crystals Monte Carlo Coarse-Grained Simulation Mean Field Theory Elasticity Orientational Order
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=kent1334550704

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-kent13345507042021-08-03T05:38:02Z Self-Assembly, Elasticity, and Orientational Order in Soft Matter Geng, Jun Condensed Matter Physics Physics Liquid Crystals Monte Carlo Coarse-Grained Simulation Mean Field Theory Elasticity Orientational Order <p>In this dissertation, I present four studies of soft matter: tetratic and nematic phases of two-dimensional liquid crystals, elasticity of asymmetric thin films, morphology of vesicles with nematic in-plane order, and defect pair annihilation in vesicles with xy in-plane order. Computer simulations and analytical calculations are used to study the problems.</p><p>In the first project, we propose a model for the statistical mechanics of particles with almost four-fold symmetry, which is weakly broken down to two-fold. We introduce a coefficient to characterize the symmetry breaking, and find that the tetratic phase can still exist even if this parameter is up to a substantial value. Through a Landau expansion of the free energy, we calculate the mean-field phase diagram, which is similar to the result of a previous hard-particle excluded-volume model. To verify our mean-field calculation, we develop a Monte Carlo simulation of spins on a triangular lattice. The results of the simulation agree very well with the Landau theory.</p><p>In the second part, we study the deformation of a thin polymer film by a change in the target metric tensor. In this problem, unlike earlier work by other researchers in this field, the target metric is asymmetric between the two sides of the film. Changing this metric induces a curvature of the film, which may be curvature into a partial cylinder or a partial sphere. We calculate the elastic energy for each of these shapes, and show that the sphere is favored for films smaller than a critical size, which depends on the film thickness, while the cylinder is favored for larger films.</p><p>In the third section, we develop a coarse-grained (CG) model to study the shape of vesicles with tangent-plane nematic order. The CG particles can self-assemble to form three dimensional vesicles and carry a tangent-plane nematic order at low temperature. As the strength of the coupling between nematic order and vesicle curvature increases, the vesicles show a morphology transition from spherical to prolate and finally to a tube. We also calculate the interesting shape and defect arrangement around the tips of the prolate vesicle.</p><p>Finally, we use a modified CG model to study the role of topological defects in the formation of complex morphologies in giant unilamellar vesicles during the transition from the in-plane isotropic phase (L<sub>α</sub>) to in-plane xy order phase (L<sub>β'</sub>). The studies show that such defects induce local membrane curvature which in turn inhibits their diffusion, arresting defect pair-annihilation and trapping the resulting complex morphology in a deeply metastable state. These simulation results suggest that kinetic competition between defect motion and annihilation and the evolution of membrane curvature can produce stable complex vesicle morphologies quite different from those predicted by previous theories.</p> 2012-04-16 English text Kent State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=kent1334550704 http://rave.ohiolink.edu/etdc/view?acc_num=kent1334550704 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Condensed Matter Physics Physics Liquid Crystals Monte Carlo Coarse-Grained Simulation Mean Field Theory Elasticity Orientational Order
spellingShingle	Condensed Matter Physics Physics Liquid Crystals Monte Carlo Coarse-Grained Simulation Mean Field Theory Elasticity Orientational Order Geng, Jun Self-Assembly, Elasticity, and Orientational Order in Soft Matter
author	Geng, Jun
author_facet	Geng, Jun
author_sort	Geng, Jun
title	Self-Assembly, Elasticity, and Orientational Order in Soft Matter
title_short	Self-Assembly, Elasticity, and Orientational Order in Soft Matter
title_full	Self-Assembly, Elasticity, and Orientational Order in Soft Matter
title_fullStr	Self-Assembly, Elasticity, and Orientational Order in Soft Matter
title_full_unstemmed	Self-Assembly, Elasticity, and Orientational Order in Soft Matter
title_sort	self-assembly, elasticity, and orientational order in soft matter
publisher	Kent State University / OhioLINK
publishDate	2012
url	http://rave.ohiolink.edu/etdc/view?acc_num=kent1334550704
work_keys_str_mv	AT gengjun selfassemblyelasticityandorientationalorderinsoftmatter
_version_	1719422780311601152

Self-Assembly, Elasticity, and Orientational Order in Soft Matter

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