Computer Simulations of Liquid Crystals and Polymers: Proceedings of the NATO Advanced Research Workshop on Computational Methods for Polymers and Liquid Crystalline Polymers Erice, Italy 16–22 July 2003

368 Pages·2005·12.17 MB·English

by  Cesare Chiccoli, Paolo Pasini, Gregor Skačej (auth.), Paolo Pasini, Claudio Zannoni, Slobodan Žumer (eds.)

Computer Simulations of Liquid Crystals and
Polymers
NATO Science Series
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Series II: Mathematics, Physics and Chemistry-Vol. 177
Computer Simulations of Liquid
Crystals and Polymers
edited by
Paolo Pasini
Istituto Nazionale di Fisica Nucleare,
Bologna, Italy
Claudio Zannoni
Universitàdi Bologna,
Italy
and
Slobodan Zumer
University of Ljubljana,
Slovenia
Kluwer Academic Publishers
Dordrecht / Boston / London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the NATO Advanced Research Workshop on
Computational Methods for Polymers and Liquid Crystalline Polymers
Erice, Italy
16-22 July 2003
A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 1-4020-2759-1 (PB)
ISBN 1-4020-2758-3 (HB)
ISBN 1-4020-2760-5 (e-book)
Published by Kluwer Academic Publishers,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
Sold and distributed in North, Central and South America
by Kluwer Academic Publishers,
101 Philip Drive, Norwell, MA 02061, U.S.A.
In all other countries, sold and distributed
by Kluwer Academic Publishers,
P.O. Box 322, 3300 AH Dordrecht, The Netherlands.
Printed on acid-free paper
All Rights Reserved
©2005 Kluwer Academic Publishers
No part of this work may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording or otherwise, without written permission from the Publisher, with the exception
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and executed on a computer system, for exclusive use by the purchaser of the work.
Printed in the Netherlands.
CONTENTS
Preface
xin
1 Lattice spin models of polymer—dispersed liquid crystals 1
Cesare Chiccoli, Paolo Pasini, Gregor Skacej, Slobodan Zumer, and
Claudio Zannoni
Introduction 1
1 Polymer-dispersed liquid crystals 2
2 The simulation method 3
2.1 The PDLC simulation model 4
2.2 Molecular ordering 5
3 2H NMR 7
3.1 Orientational fluctuations 10
3.2 Translational diffusion 13
4 External field effects 15
4.1 Radial droplet 15
4.2 Bipolar droplet 18
5 Many-droplet sample 21
6 Conclusions 23
Nematics with dispersed polymer networks: from lattice
spin models to experimental observables 27
Cesare Chiccoli, Paolo Pasini, Gregor Skacej, Slobodan Zumer, and
Claudio Zannoni
Introduction 27
1 Aligning ability of the network 29
1.1 Planar anchoring 31
1.2 Homeotropic anchoring: topological defects 32
1.3 2H NMR spectra 34
VI
2 External field-induced switching 37
2.1 Regular fiber array 37
2.2 Irregular fiber array 41
2.3 Experimental observables and network irregularity 45
3 Pretransitional ordering in the isotropic phase 49
4 Conclusions 53
3 Computer simulations of liquid crystal polymers and
dendrimers 57
Mark R. Wilson, Lorna M. Stimson, Jaroslav M. Ilnytskyi, and
Zak E. Hughes
Introduction 57
1 Simulation Models 59
1.1 Atomistic Models 59
1.2 Simplified models for polymers and liquid crystals 60
2 Hybrid Models 63
3 Side chain liquid crystalline polymers 64
4 Main chain liquid crystalline polymer 66
5 Carbosilane liquid crystalline dendrimers 69
5.1 Hybrid Gay-Berne/Lennard-Jones model 69
5.2 Coarse-grained model 75
6 Summary 78
4 Monte Carlo simulations of liquids of mesogenic
oligomers 83
Michele Vacatello and Manuela Vacatello
Introduction 83
Trimers with polymethylene spacers 85
1.1 Models and methods 85
1.2 Thermal behavior 90
1.3 Orientational order in the nematic liquids 91
1.4 Conformational changes at the nematic/isotropic tran-
sition 93
2 Dimers of series I 99
3 Conclusions 105
Vll
5 Molecular arrangements in polymer-nanofiller systems 109
Michele Vacatello and Manuela Vacatello
Introduction 109
1 Simulations of dense systems 111
1.1 Models and methods 111
1.2 The filler/polymer interface 113
1.3 Chain conformation 116
1.4 Molecular arrangements 117
1.5 Predicting the molecular arrangements 122
2 Simulations of phantom chains 125
3 Conclusions 132
6 Dissipative particle dynamics approach to nematic
polymers 135
Antonino Polimeno, Alexandre Gomes, and Assis Farinha Martins
Introduction 135
1 Dissipative Particle Dynamics 136
2 Methodology 137
3 Standard semi-rigid segments 139
4 An alternative approach 142
5 Summary 144
7 Some things we can learn from chemically realistic
polymer melt simulations 149
Wolfgang Paul, Stephan Krushev, Grant D. Smith, Oleg Borodin, and
Dmitry Bedrov
Introduction 149
1 Quantitative Comparison to Experiment 150
1.1 NMR Experiments 151
1.2 Neutron Scattering Experiments 155
1.3 Dielectric Relaxation Experiments 157
2 Changing the model Hamiltonian 162
3 Summary 168
Vlll
8 Monte Carlo simulations of semi-flexible polymers 171
Wolfgang Paul, Marcus Muller, Kurt Binder, Mikhail R. Stukan, and
Viktor A. Ivanov
Introduction 171
1 State Diagram of a Semi-flexible Chain 172
1.1 Mean Field Scaling Theory 174
1.2 State Diagram 176
2 Solutions of Semi-flexible Chains 179
3 Summary 188
9 Macromolecular mobility and internal viscosity.
The role of stereoregularity 191
Giuseppe Allegra and Sergio Bruckner
Introduction 191
1 Internal viscosity 193
2 Recent experimental investigations 194
3 Steric hindrance to rotational propagation 195
3.1 Isotactic Polystyrene (i-PS) 195
3.2 Syndiotactic Polystyrene (s-PS) 198
4 Some concluding remarks on internal viscosity and steric rota-
tional hindrance 199
10 Protein adsorption on a hydrophobic graphite surface 203
Giuseppina Raffaini and Fabio Ganazzoli
Introduction 203
1 Short background of theoretical and simulation methods 204
2 Simulations details 205
3 Initial adsorption stage in the dielectric medium 208
4 Final adsorption stage by molecular dynamics in the dielectric
medium 210
5 Kinetics of surface spreading 212
6 Hydration of the adsorbed protein fragments 215
7 Conclusions and outlook to future work 216
IX
11 Multiscale simulation of liquid crystals 221
Orlando Guzman, Sylvain Grollau, Evelina B. Kim,
and Juan J. de Pablo
Introduction 221
1 A multiscale model for LC-based sensors 224
1.1 Molecular simulations 224
1.2 Dynamic Field Theory 229
2 Clusters of particles 231
2.1 Mapping of simulation and field theory length scales 231
2.2 Sphere/substrate interactions 233
2.3 Two particle systems 235
3 Ordering kinetics in a LC-based biosensor 240
4 Conclusion 245
12 Polymer chains and networks in narrow slits 249
Giuseppe Allegra, Guido Raos, and Carlo Manassero
Introduction 249
1 Compressed polymer networks 251
1.1 A Gaussian chain in a harmonic potential 251
1.2 The two-dimensional network 254
1.3 Numerical results 256
2 Polymer-mediated adhesion 257
2.1 The model 257
2.2 The transfer matrix 258
2.3 Statistical population of loops and bridges 260
2.4 Free energy, elastic forces and moduli 263
3 Conclusions 266
13 Rotation and deformation of polymer molecules in
solutions subjected to a shear flow 269
Siegfried Hess and Gary P. Morriss
Introduction 270
1 Angular Velocity and Deformation 271
2 A Simple Model 273
3 Rotation and Deformation 274