Molecular Gels (eBook)

Materials with Self-Assembled Fibrillar Networks

Richard G. Weiss, Pierre Terech (Herausgeber)

eBook Download: PDF

2006 | 2006
XV, 978 Seiten
Springer Netherland (Verlag)
978-1-4020-3689-7 (ISBN)

Infos

'Molecular Gels: Materials with Self-Assembled Fibrillar Networks' is a comprehensive treatise on gelators, especially low molecular-mass gelators and the properties of their gels. The structures and modes of formation of the self-assembled fibrillar networks (SAFINs) that immobilize the liquid components of the gels are discussed experimentally and theoretically. The spectroscopic, rheological, and structural features of the different classes of low molecular-mass gelators are also presented. Many examples of the application of the principal analytical techniques for investigation of molecular gels (including SANS, SAXS, WAXS, UV-vis absorption, fluorescence and CD spectroscopies, scanning electron, transmission electron and optical microscopies, and molecular modeling) are presented didactically and in-depth, as are several of the theories of the stages of aggregation of individual low molecular-mass gelator molecules leading to SAFINs. Several actual and potential applications of molecular gels in disparate fields (from silicate replication of nanostructures to art conservation) are described. Special emphasis is placed on perspectives for future developments.

This book is an invaluable resource for researchers and practitioners either already researching self-assembly and soft matter or new to the area. Those who will find the book useful include chemists, engineers, spectroscopists, physicists, biologists, theoreticians, and materials scientists.

Richard G. Weiss is Professor of Chemistry, Department of Chemistry, Georgetown University, Washington, DC, USA.

Pierre Terech is Research Director, CNRS - Atomic Energy Center - Grenoble University, Grenoble, France.

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"e;Molecular Gels: Materials with Self-Assembled Fibrillar Networks"e; is a comprehensive treatise on gelators, especially low molecular-mass gelators and the properties of their gels. The structures and modes of formation of the self-assembled fibrillar networks (SAFINs) that immobilize the liquid components of the gels are discussed experimentally and theoretically. The spectroscopic, rheological, and structural features of the different classes of low molecular-mass gelators are also presented. Many examples of the application of the principal analytical techniques for investigation of molecular gels (including SANS, SAXS, WAXS, UV-vis absorption, fluorescence and CD spectroscopies, scanning electron, transmission electron and optical microscopies, and molecular modeling) are presented didactically and in-depth, as are several of the theories of the stages of aggregation of individual low molecular-mass gelator molecules leading to SAFINs. Several actual and potential applications of molecular gels in disparate fields (from silicate replication of nanostructures to art conservation) are described. Special emphasis is placed on perspectives for future developments.This book is an invaluable resource for researchers and practitioners either already researching self-assembly and soft matter or new to the area. Those who will find the book useful include chemists, engineers, spectroscopists, physicists, biologists, theoreticians, and materials scientists.

Inhalt

TABLE OF CONTENTS 7
LIST OF CONTRIBUTORS 11
INTRODUCTION 16
References 26
THEORY 30
Chapter 1 THEORY OF MOLECULAR ASSOCIATION AND THERMOREVERSIBLE GELATION 32
1. Thermodynamic Theory of Network-Forming Liquid Mixtures 33
1.1. Models of Associating Mixtures 33
1.2. Free Energy and Distribution Function of Aggregates 35
1.3. Phase Separation, Stability Limit and Other Solution Properties 41
2. Some Important Examples of Non-Gelling Associating Mixtures 42
2.1. Dimer Formation 43
2.2. Linear Association and Ring Formation 46
2.3. Side-Chain Association 49
2.4. Hydration in Aqueous Polymer Solutions and Closed- Loop Miscibility Gap 54
2.5. Hydrogen-Bonded Liquid-Crystalline Supramolecules 56
3. Gelling Solutions and Mixtures 59
3.1. Micellization and Gelation 59
3.2. Gelation by Pairwise Association 63
3.3. Multiple Association 73
3.4. Structure of the Networks with Multiple Junctions 78
3.5. Mixtures of Associative Molecules – Gelation with Co- Networks 84
4. Conclusions and Perspectives for the Future 89
References 89
Chapter 2 GROWTHAND CHIRALITYAMPLIFICATION IN HELICAL SUPRAMOLECULAR POLYMERS 94
1. Introduction 94
2. Helical Aggregation 95
3. Discotics 97
4. Linear Self-Assembly 98
5. ATwo-State Model 100
6. Aggregate Ends 101
7. Chirality Ampli.cation 105
8. Sergeants and Soldiers 106
9. Conclusions and Perspectives for the Future 109
References 110
Chapter 3 SELF- ASSEMBLING PEPTIDE GELS 114
1. Introduction 114
2. Theoretical Model of Self-Assembling Chiral Rod- Like Units 115
3. Experiments Illustrating Predictions of the Model 3.1. P11- 1: CH3CO- Gln- Gln- Arg- Gln- Gln- Gln- Gln- Gln- Glu- Gln- Gln- NH2 120
4. Stabilization by Twist 127
5. Wider Implications of the Model 129
6. Peptide Gels are Nematic Hydrogels 132
7. Prospects for Engineering Functional Hydrogels 134
8. Conclusions and Perspectives for the Future 142
References 143
Chapter 4 KINETICS OF NUCLEATION, AGGREGATION AND AGEING 146
1. Introduction 146
2. Some Basic Thermodynamic Concepts 147
3. Basic Concepts of the Theory of Nucleation and Cluster Growth 149
3.1. The Origin of Metastability: Critical Clusters 149
3.2. The Steady-State Nucleation Rate 152
3.3. Methods of Determination of theWork of Critical Cluster Formation 155
3.4. Nucleation and Simultaneous Growth: The Kolmogorov- Avrami Equation 166
3.5. Depletion Effects and the Overall Course of First- Order Phase Transitions 168
4. Spinodal Decomposition 169
5. Secondary Aggregation, Coarsening and Ageing 173
6. Overview 175
References 175
Chapter 5 SOFT GLASSY RHEOLOGY 176
1. Introduction 177
2. Rheology 178
2.1. Constitutive Properties 178
2.2. Step Strain 179
2.3. Linearity 179
2.4. Behaviour of the Linear Response Function 180
2.5. Creep Compliance 180
2.6. Viscoelastic Spectra 180
2.7. Steady State Response: The Flow Curve 182
2.8. Ageing 183
3. The SGR Model 185
3.1. Constitutive Equation 188
3.2. Tensorial SGR Model 189
3.3. Rheological PropertiesWithout Ageing 190
4. Rheological Ageing: Imposed Strain 191
4.1. Linear Response 192
4.2. Nonlinear Response 197
5. Rheological Ageing: Imposed Stress 199
5.1. Linear Response 199
5.2. Nonlinear Response 201
6. Conclusions and Perspectives for the Future 203
Acknowledgments 205
References 206
Chapter 6 RHEOLOGICAL CHAOS IN WORMLIKE MICELLES AND NEMATIC HYDRODYNAMICS 208
1. Introduction 208
2. Deterministic Chaos in Viscoelastic Materials in Shear Flow 210
2.1. Experiments 210
2.2. Theories 217
3. Spatio-temporal Rheological Oscillations and Chaotic Dynamics 3.1. Theoretical Investigations of Spatio- temporal Rheochaos 225
4. Proposed Experiments 233
Acknowledgments 233
References 234
Chapter 7 WETTING OF FIBERS 238
1. Introduction 238
2. The Rayleigh-Plateau Instability 239
3. Drop Shapes 240
3.1. Axisymmetric Shapes 241
3.2. Asymmetric Droplets 242
4. Heterogeneous Fiber 245
5. Invasion of a Network of Fibers 246
6. Conclusions and Perspectives for the Future 251
References 251
TECHNIQUES 254
Chapter 8 GEL FORMATION: PHASE DIAGRAMS USING TABLETOP RHEOLOGYAND CALORIMETRY 256
1. Introduction 256
2. Detecting the Sol-Gel Transition by Tabletop Rheology 257
2.1. Tube Inversion 258
2.2. Falling of Spheres 260
2.3. Rise of Bubbles 261
2.4. Other Methods 261
3. Thermodynamics of Gelation: Sol-Gel Transition by Calorimetry 262
3.1. First- and Second-Order Phase Transitions 263
3.2. The Question of Gelation 263
3.3. Calorimetry of the Sol-Gel Transition 265
3.4. Gelation Temperature vs. Gelator Concentration 265
4. Conclusions and Perspectives 266
References 267
Chapter 9 DIRECT- IMAGINGAND FREEZE-FRACTURE CRYO- TRANSMISSION ELECTRON MICROSCOPY OF MOLECULAR GELS 268
1. Introduction 268
2. Cryo-TEM 269
3. Cryo-TEM Investigations of LMOG Gels 273
4. Conclusions and Perspectives for the Future 286
References 286
Chapter 10 MOLECULAR GELS AND SMALL-ANGLE SCATTERING 290
1. Foreword 291
2. Introduction 291
3. Basic Principles 294
4. Form-Factors of Rod-Like Scatterers 297
4.1. Plain Fibers 297
4.2. Short Rods 305
5. Semi-Rigid Fibers 307
6. Fibers with Anisometric Sections 308
6.1. Rectangular Sections 309
6.2. Elliptical Cross-Sections 309
7. Tubes 310
8. Helices 313
9. Scattering by the Junction Zones 315
9.1. Form-Factor of a Disk 315
9.2. Spherulitic Nodes 317
9.3. Random Nodes: Debye-Büeche Context 317
9.4. Ideally Homogeneous Networks 318
9.5. Fractal Context 319
9.6. Orientation Correlated Domains 320
10. Structure Factor Peak in Poorly Organized Fibrillar Scatterers 322
11. Oriented Fibers 326
11.2. Shear Alignment 327
12. Real Space Data 331
13. Kinetic Studies 332
14. Useful Hints for a Standard SANS Investigation of Molecular Gels 334
15. Conclusions 336
References 337
Chapter 11 X- RAYDIFFRACTION OF POORLYORGANIZED SYSTEMS AND MOLECULAR GELS 340
1. Introduction 340
2. Long Range Ordering 342
2.1. Diffraction and Diffuse Scattering 342
2.2. The Crystal Structure 342
3. Single Crystal Diffraction 344
3.1. The Structure Factor 345
3.2. Crystal Structure Solution 346
4. Powder Diffraction 352
4.1. Structure Determination from Powders 353
4.2. Multi-phases and Quantification by Profile Refinement Techniques 359
4.3. Microstructures 360
5. X-Rays and Neutrons 362
6. Applications of Diffraction 363
6.1. Partially Disordered Compounds: Pharmaceutical Molecules 363
6.2. Molecular Gels 368
7. Conclusions 375
References 376
Chapter 12 OPTICAL SPECTROSCOPIC METHODS AS TOOLS TO INVESTIGATE GEL STRUCTURES 378
1. Introduction 378
2. Electronic Absorption and Emission Spectroscopy 2.1. General Considerations Concerning UV- vis and Fluorescence Spectroscopy 379
3. Infrared Spectroscopy 422
3.1. General Considerations 422
3.2. Selected Examples Illustrating the Application of Infrared Spectroscopy to the Study of Gel Structures 424
3.3. IR Absorption Spectroscopy of 2,3-Di-n-decyloxyanthracene (DDOA). Assignment of Vibration Bands and Dichroic Absorption 434
4. Conclusions and Perspectives for the Future 440
References 440
Chapter 13 CIRCULAR DICHROISM FOR STUDYING GEL- LIKE PHASES 446
1. Introduction 446
2. Technique 447
2.1. How to Obtain CD Spectra 448
2.2. Experimental Problems 449
3. Applications to the Study of Gel-Like Phases 450
4. Conclusions and Perspectives for the Future 460
References 460
SYSTEMS – ORGANOGELS 463
Chapter 14 LOW MOLECULAR-MASS ORGANIC GELATORS 464
1. Introduction 464
2. Classification of Organic Gelators 465
2.1. Alkane Gelators 466
2.2. Organic Gelators with One Heteroatom 466
2.3. Organic Gelators with Two Heteroatoms 485
2.4. Organic Gelators Containing Three Heteroatom Types 513
2.5. Polymerizable Organic Gelators 515
2.6. Two Component Organic Gelators 518
2.7. Inorganic and Organometallic Gelators 528
2.8. Liquid-Crystalline Gels 529
2.9. Latent Gelators 534
2.10. Microemulsion-based Gelators 536
2.11. Miscellaneous Organic Gelators 538
3. The Role of Liquid in Gelation by LMOGs 542
4. Conclusions and Perspectives for the Future 550
Acknowledgments 552
References 552
Chapter 15 DESIGN AND FUNCTION OF LOW MOLECULAR- MASS ORGANIC GELATORS ( LMOGs) BEARING STEROID AND SUGAR GROUPS 568
1. Introduction 568
2. Steroid Derivatives for Gelating Organic Liquids 569
2.1. Introduction 569
2.2. Structural Variations of Steroid-Based Gelators and their Analyses 569
2.3. Functional Applications of Cholesterol-Based LMOGs 572
2.4. Conclusions 578
3. Sugar Derivatives for Gelating Liquids 579
3.1. Introduction 579
3.2. Structural Variations of Sugar-Based Gelators 579
3.3. Dual-Component Gelators Based on Charge-Transfer Phenomena 582
3.4. Combinatorial Approaches for Finding Gelators and Building Integrated Systems Utilizing a Sugar Library 582
3.5. Conclusions 584
4. Other Related LMOGs 585
4.1. Nucleobase Gelators 585
4.2. Vancomycin Gelator 588
5. Perspectives for the Future 589
References 589
Chapter 16 SAFIN GELS WITHAMPHIPHILIC MOLECULES 592
1. Introduction 592
2. Amphiphilic Molecules 593
2.1. Amphiphilicity 593
2.2. Amphiphilic Molecules 593
3. Gels with Amphiphilic Molecules 596
3.1. Characteristics of SAFIN Gels with Amphiphilic Molecules 597
3.2. Amphiphilic Molecules which Form SAFIN Gels 599
3.3. Chiral Supramolecular Structures 603
4. Gemini Amphiphilic Molecules 606
4.1. Definitions 606
4.2. Particularities of Gemini Molecules 607
4.3. What Kind of Gemini Molecules Form Gels? 608
5. Conclusions and Perspectives for the Future 614
Acknowledgment 616
References 617
SYSTEMS – HYDROGELS 626
Chapter 17 ADVANCES IN MOLECULAR HYDROGELS 628
1. Introduction 628
2. Historical Perspectives 630
3. Amino Acid and Oligopeptide Based Hydrogelators 631
4. ß-Peptide Based Hydrogelators 640
5. Carbohydrate Based Gelators 643
6. Hydrogelators from Bola-amphiphiles and Gemini Surfactants 646
7. Miscellaneous Hydrogelators 649
8. Bile Acid Based Hydrogelators 651
9. Structural and Dynamic Aspects of Hydrogels 655
10. Application of Hydrogels in Materials Science 657
11. Perspectives for the Future 658
Abbreviations 659
Acknowledgments 659
References 659
Chapter 18 AQUEOUS GELS MADE OF CHIRAL LIPID- AND PORPHYRIN- AMPHIPHILES 664
1. Introduction 664
2. Electron Microscopy in Water and Toluene 664
3. The Effect of Charge Repulsion in Water 666
4. Stereochemistry and the Chiral Bilayer Effect 668
5. Viscoelastic Gels inWater 675
6. Bolaamphiphiles 676
7. Conclusions 676
References 678
ANALYSES OF SPECIFIC SYSTEMS 681
Chapter 19 RHEOLOGY OF WORMLIKE MICELLES: EQUILIBRIUM PROPERTIES AND SHEAR BANDING TRANSITIONS 682
1. Introduction 682
2. Equilibrium Properties 684
2.1. Theoretical Background 684
2.2. Physical Chemistry ofWormlike Micelles and Related Systems 685
2.3. Flexibility ofWormlike Micelles 689
2.4. Phase Behavior 693
2.5. Linear Rheology and Scaling 695
2.6. Concluding Remarks on the Equilibrium Properties 700
3. Shear Banding Transition in Concentrated and Semi- Dilute Regimes 701
3.1. Isotropic-to-Nematic Transition in the Concentrated Regime 702
3.2. Shear Banding in Semi-Dilute Regime 711
3.3. Theories and Interpretations 717
4. Conclusions and Perspectives for the Future 721
Acknowledgments 722
References 723
Chapter 20 CRYO- TEM, X-RAY DIFFRACTION AND MODELING OFAN ORGANIC HYDROGEL 736
1. Introduction 736
2. Techniques 737
3. Modeling Gel Structure 738
3.1. Molecular Structure 739
3.2. Nanometer Structure 739
3.3. Micrometer Structure 743
4. A Case Study 744
4.1. Cryo-Transmission Electron Microscopy 746
4.2. X-ray Diffraction 747
4.3. Modeling 749
5. Perspectives for the Future 752
Acknowledgments 753
References 753
Chapter 21GELATION OFA LIQUID-CRYSTALLINE La PHASE INDUCED BY THE PROLIFERATION OF TOPOLOGICAL DEFECTS 758
1. Introduction 759
1.1. Basic De.nitions 759
1.2. Topological Defects in an Organized Phase Can Induce Gelation 762
1.3. Scope and Outline of the Chapter 762
2. Gelation of a Lamellar La Phase by Additionof Peg-Lipids 763
2.1. Description of the System and its Components 763
2.2. Phase Diagram and Gelation 764
2.3. Observations of Samples in Polarized Light 766
2.4. Electron Microscopy 767
2.5. X-Ray Scattering 768
2.6. Rheology 770
2.7. Model and Discussion 772
3. A New Class of Gels 774
3.1. Extensive Chemical Modi.cation of PEG-lipids Does not Affect Their Gelating Power 774
3.2. Double-End-Anchored PEG-Surfactants also Induce Gelation 776
4. Generalization 780
4.1. Gelation of a Lamellar Phase by Addition of Particles 780
4.2. Gelation of Other Mesophases 780
4.3. Ringing Gels 781
5. Conclusions and Perspectives for the Future 782
Acknowledgments 782
References 782
APPLICATIONS 786
Chapter 22 GELS OF LIQUID CRYSTALS AND ION- CONDUCTING FLUIDS 788
1. Introduction 788
2. Liquid Crystal and Ion Conducting Gels for Electro Optical Devices 789
2.1. Gels with Chemically Cross-Linked Networks 789
2.2. Photopolymerization of Acrylates 789
2.3. Liquid Crystal Gels 790
2.4. Ion Conducting Gels 796
References 806
Chapter 23 ELECTRON CONDUCTINGAND MAGNETO- SENSITIVE GELS 808
1. Introduction 808
1.1. Electron Conduction in Conducting Polymers 809
1.2. Conducting Gels 813
2. Molecular Gels as Templating Media for Electronic Materials 820
2.1. Polymerizable LMOGs 821
2.2. Templating of Inorganic Structures 821
2.3. Spatial Organization of Semiconductor Nanoparticles 823
3. Magnetosensitive Gels 823
4. Conclusions and Perspectives for the Future 825
Acknowledgments 825
References 825
Chapter 24 PHOTORESPONSIVE GELS 832
1. Luminescent Gels 832
1.1. General Considerations 832
1.2. Luminescent Organogels and Energy Transfer 839
2. Phototunable Gels 850
2.1. General Considerations 851
2.2. Systems 852
2.3. Photochromic Gels Based on Polymers 856
2.4. Photochromic Properties Modulated by the Sol-Gel Transitions Using LMOGs 858
2.5. Irreversible, Photo-Induced Phase Transitions Using LMOGs 859
2.6. Reversible, Photo-Induced Phase Transitions Using LMOGs 861
3. Conclusions and Perspectives for the Future 865
Acknowledgments 866
References 866
Chapter 25 GELS OF LOW MOLECULAR-MASS ORGANIC GELATORS AS TEMPLATES FOR TRANSCRIPTION 872
1. Introduction 873
2. The Basics of Sol-Gel Chemistry 875
2.1. Hydrolysis 877
2.2. Condensation 878
3. Transcription of the Gelator Template 879
3.1. Gelators Possessing Covalently Attached, Positively Charged Centers 880
3.2. Gelators Containing Non-Covalently Attached, Positively Charged Centers 883
3.3. Gelators Containing Hydrogen-Bond Donating Amine Groups 885
3.4. Gelators with Different Structural Features 887
3.5. Outlook for the Future 889
4. Shapes of Transcribed Materials 890
4.1. Transcription of Cholesterol-Based Gelators 892
4.2. Transcription of Sugar-Based Gelators 897
4.3. Transcription of Cyclohexane-Based Gelators 901
4.4. Perspectives for the Future 903
5. General Conclusions and Challenges for the Future 903
References 905
Chapter 26 RESPONSIVE MOLECULAR GELS 910
1. Introduction 910
1.1. Responsive Chemical Gels 911
1.2. Responsive Physical Gels 912
1.3. Triggering Signals and Expected Responses 912
1.4. Boundaries and Limitations 914
2. Chemo-Responsive Gels 914
2.1. Chemo-Responsive Gels by Host-Guest Complexation 915
2.2. Metal-Ion Responsive Gels 920
2.3. Responsive Gel Systems by Uptake and Release of Gasses 922
2.4. Gel-Sol Phase Transitions Triggered by pH Changes 923
3. Physico-Responsive Gels 929
3.1. An Unusual Temperature Responsive LMOG Gel 929
3.2. Reponses to Mechanical Stress 930
3.3. Light-Responsive Gels 932
4. Conclusions and Perspectives for the Future 939
References 940
Chapter 27 GELS AS CLEANING AGENTS IN CULTURAL HERITAGE CONSERVATION 944
1. Introduction 944
2. Polyacrylic Acid-Based Gels in Cultural Heritage Conservation 948
3. Application and Removal of Gels from Painted Surfaces 949
4. Future Perspectives 951
References 951
COLOR SECTION 955
INDEX 964

Produkt-Details

• Erscheint lt. Verlag: 30.6.2006
• Zusatzinfo: XV, 978 p.
• Verlagsort: Dordrecht
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie ► Physikalische Chemie
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Atom- / Kern- / Molekularphysik
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Thermodynamik
• Themenwelt: Technik
• Schlagworte: Absorption • Amino acid • fibrillar network • Lipid • Molecular Gels • RSI • Self-Assembly • soft matter • Sol-Gel
• ISBN-10: 1-4020-3689-2 / 1402036892
• ISBN-13: 978-1-4020-3689-7 / 9781402036897