Table Of ContentH
i
r
s
t
Fundamentals of
F
Physical sciences
u
n
d
Soft
a
Soft materials such as liquid crystals, polymers, biomaterials, and colloidal m
systems touch every aspect of our lives. Not surprisingly, the rapid growth e
n
of these fields over the past few decades has resulted in an explosion of soft
t
a
matter research groups worldwide. Fundamentals of Soft Matter Science
l Matter
s
introduces and explores the scientific study of soft matter and molecular self-
o
assembly, covering the major classifications of materials, their structure and
f
characteristics, and everyday applications.
S
o
Designed for beginners to the field with a basic scientific background, this f Science
t
readable book emphasizes conceptual understanding, minimizing detailed
M
mathematical derivations. Each chapter is dedicated to a different group of
soft materials, including liquid crystals, surfactants, polymers, colloids, and a
soft biomaterials. Each subject is broken down into the essential concepts: t
t
material structures and physical characteristics, some simple theoretical ideas, e
and important experimental methods. The book emphasizes commonly used r
experimental techniques and practical applications. Full color illustrations and S
photographs are incorporated throughout to help describe the systems and c
key concepts. i
e
n
c
e
Linda S. Hirst
K11369
ISBN: 978-1-4398-2775-8
90000
www.crcpress.com
9 781439 827758
w w w. c r c p r e s s . c o m
K11369_COVER_final_revised.indd 1 10/19/12 12:52 PM
Fundamentals of
Soft
Matter
Science
Fundamentals of
Soft
Matter
Science
Linda S. Hirst
With photography and illustrations by Trevor P. Hirst
CRC Press
Taylor & Francis Group
6000 Broken Sound Parkway NW, Suite 300
Boca Raton, FL 33487-2742
© 2013 by Taylor & Francis Group, LLC
CRC Press is an imprint of Taylor & Francis Group, an Informa business
No claim to original U.S. Government works
Version Date: 20130103
International Standard Book Number-13: 978-1-4665-9092-2 (eBook - PDF)
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This book is dedicated my Dad, Bill Matkin,
who inspired my love of books
Contents
Preface ............................................................................................................................................................................................................xiii
Acknowledgments ..................................................................................................................................................................................xv
About the Author ...................................................................................................................................................................................xvii
About the Illustrator ...............................................................................................................................................................................xix
Chapter 1 Introduction ....................................................................................................................................................................1
Learning Objectives ...................................................................................................................................................1
1.1 What Is Soft Matter? ....................................................................................................................................2
1.2 Basic Thermal Physics ................................................................................................................................3
1.2.1 Thermal Equilibrium ................................................................................................................3
1.2.2 Phase Transitions .......................................................................................................................4
1.2.3 Solids, Liquids, and Gases .....................................................................................................6
1.2.4 The Ideal Gas ................................................................................................................................7
1.3 Intermolecular Forces ................................................................................................................................9
1.3.1 The van der Waals Attraction ............................................................................................9
1.3.2 Hard Sphere Repulsion ........................................................................................................10
1.3.3 Electrostatic Forces ................................................................................................................11
1.3.4 The van der Waals Equation of State (for a Nonideal Gas) .............................11
1.3.5 Hydrophobic Effects and the Hydrogen Bond .....................................................11
1.4 Diffusion and Random Walks .............................................................................................................14
1.5 Self-Assembly ...............................................................................................................................................16
1.6 The Phase Diagram ...................................................................................................................................18
1.6.1 The Clausius–Clapeyron Equation ................................................................................20
1.7 Aggregation and Assembly .................................................................................................................21
1.7.1 Power Laws and Fractals.....................................................................................................22
1.8 Mechanical Properties of Soft Matter ............................................................................................25
1.8.1 Stress and Strain .......................................................................................................................26
Questions .......................................................................................................................................................................29
The Concept of Soft Materials and Their Characteristics ...................................................29
Review of Thermal Physics ...................................................................................................................30
Review the Mechanical Properties of Materials ......................................................................30
References ......................................................................................................................................................................31
Further Reading ..........................................................................................................................................................31
Chapter 2 Liquid Crystals ..............................................................................................................................................................33
Learning Objectives .................................................................................................................................................33
2.1 Introduction to Liquid Crystals ..........................................................................................................34
2.1.1 What Is a Liquid Crystal? .....................................................................................................34
2.2 Anisotropy in Liquid Crystals ...............................................................................................................34
2.3 The Order Parameter ...............................................................................................................................36
vii
viii Contents
2.4 Thermotropic and Lyotropic Liquid Crystals .............................................................................36
2.5 Birefringence in Liquid Crystals .........................................................................................................36
2.6 Defect Textures ...........................................................................................................................................38
2.7 Thermotropic Liquid Crystal Phases ...............................................................................................39
2.7.1 The Nematic Phase ...............................................................................................................40
2.7.2 The Smectic Phases ...............................................................................................................41
2.7.3 Chirality in Liquid Crystals ..................................................................................................43
2.7.4 The Cholesteric Phase .........................................................................................................44
2.7.5 The Chiral Smectic Phases ................................................................................................46
2.7.6 Other Chiral Smectic Phases ............................................................................................47
2.7.7 The Bent-Core (Banana) Phases ......................................................................................49
2.7.8 Discotic Phases .........................................................................................................................50
2.8 Experimental Techniques ......................................................................................................................51
2.8.1 Deforming Liquid Crystals .................................................................................................51
2.8.2 Polarized Optical Microscopy ..........................................................................................52
2.8.3 Electro-optical Measurements ........................................................................................55
2.8.4 The Dielectric Properties of Liquid Crystals ............................................................55
2.8.5 The Fréedericksz Transition and Measurement of the
Elastic Constants ......................................................................................................................56
2.8.6 X-ray Diffraction .......................................................................................................................58
2.8.7 Differential Scanning Calorimetry .................................................................................60
2.9 Applications of Liquid Crystals ...........................................................................................................62
2.9.1 Liquid Crystal Displays .........................................................................................................62
2.9.2 The Twisted Nematic Display ..........................................................................................64
2.9.3 Spatial Light Modulators .....................................................................................................65
2.9.4 Liquid Crystal Temperature Sensors ............................................................................65
Questions .......................................................................................................................................................................67
The Characteristics of Liquid Crystal Materials ........................................................................67
Anisotropy and Birefringence ............................................................................................................67
The Structure of Liquid Crystal Phases .........................................................................................68
Experimental Techniques and Liquid Crystal Technologies ............................................68
References ......................................................................................................................................................................69
Further Reading ..........................................................................................................................................................69
Chapter 3 Surfactants .....................................................................................................................................................................71
Learning Objectives .................................................................................................................................................71
3.1 Introduction ..................................................................................................................................................72
3.2 Types of Surfactants .................................................................................................................................72
3.3 Surface Tension and Surfactants ......................................................................................................74
3.4 Self-Assembly and Phase Behavior..................................................................................................77
3.4.1 The Micellar Phase and the Critical Micelle Concentration ...........................78
3.4.2 Other Surfactant Phases .....................................................................................................79
3.4.3 The Packing Parameter ........................................................................................................81
3.5 Membrane Elasticity and Curvature ...............................................................................................82
3.5.1 Bicontinuous Phases.............................................................................................................84
3.6 Applications of Surfactants ..................................................................................................................85
3.6.1 Detergents ...................................................................................................................................85
Contents ix
3.6.2 Detergent Foams.....................................................................................................................87
3.6.3 Emulsifiers and Emulsions ..................................................................................................88
3.6.4 Commercial Paints and Inks.............................................................................................90
3.6.5 Surfactants and Gel Electrophoresis ...........................................................................91
3.6.6 Lung Surfactant ........................................................................................................................91
3.7 Experimental Methods ...........................................................................................................................92
3.7.1 The Langmuir Trough ...........................................................................................................92
3.7.2 Measuring Surface Tension ..............................................................................................94
Questions .......................................................................................................................................................................95
Physical and Chemical Properties of Surfactants ...................................................................95
The Hydrophobic Effect .........................................................................................................................95
The Importance of Molecular Shape on Phase Structure and
Membrane Curvature ...........................................................................................................95
References ......................................................................................................................................................................96
Further Reading ..........................................................................................................................................................96
Chapter 4 Polymers ..........................................................................................................................................................................97
Learning Objectives .................................................................................................................................................97
4.1 Introduction ..................................................................................................................................................98
4.2 Early Polymers ..............................................................................................................................................98
4.3 Polymer Structure ......................................................................................................................................99
4.4 Liquid Crystal Polymers .......................................................................................................................103
4.5 Polymer Solutions ...................................................................................................................................104
4.5.1 The Ideal Chain ......................................................................................................................105
4.5.2 Excluded Volume and Solvent Effects ....................................................................107
4.5.3 The Radius of Gyration ......................................................................................................108
4.5.4 Increasing the Concentration of a Polymer Solution .....................................108
4.5.5 Stretching a Polymer Chain: The Entropic Spring .............................................110
4.5.6 Polyelectrolytes ......................................................................................................................112
4.5.7 Polymer Gels ............................................................................................................................113
4.5.8 Hydrogels ...................................................................................................................................114
4.6 The Glassy and Polymer Melt Phases ...........................................................................................115
4.7 The Mechanical Properties of Polymers.....................................................................................117
4.8 Experimental Techniques ...................................................................................................................120
4.8.1 Scattering Techniques.......................................................................................................120
4.8.2 Polymer Spectroscopy ......................................................................................................122
4.8.2.1 Fourier Transform Infrared Spectroscopy .......................................123
4.8.2.2 Raman Spectroscopy ..................................................................................123
4.8.2.3 Nuclear Magnetic Resonance ................................................................124
Questions ....................................................................................................................................................................127
Polymer Architecture ............................................................................................................................127
Polymers in Solution .............................................................................................................................127
Experimental Methods ........................................................................................................................128
References ...................................................................................................................................................................128
Further Reading .......................................................................................................................................................128
