Weiss / Terech Molecular Gels

Materials with Self-Assembled Fibrillar Networks
1. Auflage 2006
ISBN: 978-1-4020-3689-7
Verlag: Springer Netherlands
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 978 Seiten

'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.

Autoren/Hrsg.

Weiss, Richard G.

Terech, Pierre

Inhaltsverzeichnis

1;TABLE OF CONTENTS;7
2;LIST OF CONTRIBUTORS;11
3;INTRODUCTION;16
3.1;References;26
4;THEORY;30
4.1;Chapter 1 THEORY OF MOLECULAR ASSOCIATION AND THERMOREVERSIBLE GELATION;32
4.1.1;1. Thermodynamic Theory of Network-Forming Liquid Mixtures;33
4.1.1.1;1.1. Models of Associating Mixtures;33
4.1.1.2;1.2. Free Energy and Distribution Function of Aggregates;35
4.1.1.3;1.3. Phase Separation, Stability Limit and Other Solution Properties;41
4.1.2;2. Some Important Examples of Non-Gelling Associating Mixtures;42
4.1.2.1;2.1. Dimer Formation;43
4.1.2.2;2.2. Linear Association and Ring Formation;46
4.1.2.3;2.3. Side-Chain Association;49
4.1.2.4;2.4. Hydration in Aqueous Polymer Solutions and Closed- Loop Miscibility Gap;54
4.1.2.5;2.5. Hydrogen-Bonded Liquid-Crystalline Supramolecules;56
4.1.3;3. Gelling Solutions and Mixtures;59
4.1.3.1;3.1. Micellization and Gelation;59
4.1.3.2;3.2. Gelation by Pairwise Association;63
4.1.3.3;3.3. Multiple Association;73
4.1.3.4;3.4. Structure of the Networks with Multiple Junctions;78
4.1.3.5;3.5. Mixtures of Associative Molecules – Gelation with Co- Networks;84
4.1.4;4. Conclusions and Perspectives for the Future;89
4.1.5;References;89
4.2;Chapter 2 GROWTHAND CHIRALITYAMPLIFICATION IN HELICAL SUPRAMOLECULAR POLYMERS;94
4.2.1;1. Introduction;94
4.2.2;2. Helical Aggregation;95
4.2.3;3. Discotics;97
4.2.4;4. Linear Self-Assembly;98
4.2.5;5. ATwo-State Model;100
4.2.6;6. Aggregate Ends;101
4.2.7;7. Chirality Ampli.cation;105
4.2.8;8. Sergeants and Soldiers;106
4.2.9;9. Conclusions and Perspectives for the Future;109
4.2.10;References;110
4.3;Chapter 3 SELF- ASSEMBLING PEPTIDE GELS;114
4.3.1;1. Introduction;114
4.3.2;2. Theoretical Model of Self-Assembling Chiral Rod- Like Units;115
4.3.3;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
4.3.4;4. Stabilization by Twist;127
4.3.5;5. Wider Implications of the Model;129
4.3.6;6. Peptide Gels are Nematic Hydrogels;132
4.3.7;7. Prospects for Engineering Functional Hydrogels;134
4.3.8;8. Conclusions and Perspectives for the Future;142
4.3.9;References;143
4.4;Chapter 4 KINETICS OF NUCLEATION, AGGREGATION AND AGEING;146
4.4.1;1. Introduction;146
4.4.2;2. Some Basic Thermodynamic Concepts;147
4.4.3;3. Basic Concepts of the Theory of Nucleation and Cluster Growth ;149
4.4.3.1;3.1. The Origin of Metastability: Critical Clusters;149
4.4.3.2;3.2. The Steady-State Nucleation Rate;152
4.4.3.3;3.3. Methods of Determination of theWork of Critical Cluster Formation;155
4.4.3.4;3.4. Nucleation and Simultaneous Growth: The Kolmogorov- Avrami Equation;166
4.4.3.5;3.5. Depletion Effects and the Overall Course of First- Order Phase Transitions;168
4.4.4;4. Spinodal Decomposition;169
4.4.5;5. Secondary Aggregation, Coarsening and Ageing;173
4.4.6;6. Overview;175
4.4.7;References;175
4.5;Chapter 5 SOFT GLASSY RHEOLOGY;176
4.5.1;1. Introduction;177
4.5.2;2. Rheology;178
4.5.2.1;2.1. Constitutive Properties;178
4.5.2.2;2.2. Step Strain;179
4.5.2.3;2.3. Linearity;179
4.5.2.4;2.4. Behaviour of the Linear Response Function;180
4.5.2.5;2.5. Creep Compliance;180
4.5.2.6;2.6. Viscoelastic Spectra;180
4.5.2.7;2.7. Steady State Response: The Flow Curve;182
4.5.2.8;2.8. Ageing;183
4.5.3;3. The SGR Model;185
4.5.3.1;3.1. Constitutive Equation;188
4.5.3.2;3.2. Tensorial SGR Model;189
4.5.3.3;3.3. Rheological PropertiesWithout Ageing;190
4.5.4;4. Rheological Ageing: Imposed Strain;191
4.5.4.1;4.1. Linear Response;192
4.5.4.2;4.2. Nonlinear Response;197
4.5.5;5. Rheological Ageing: Imposed Stress;199
4.5.5.1;5.1. Linear Response;199
4.5.5.2;5.2. Nonlinear Response;201
4.5.6;6. Conclusions and Perspectives for the Future;203
4.5.7;Acknowledgments;205
4.5.8;References;206
4.6;Chapter 6 RHEOLOGICAL CHAOS IN WORMLIKE MICELLES AND NEMATIC HYDRODYNAMICS;208
4.6.1;1. Introduction;208
4.6.2;2. Deterministic Chaos in Viscoelastic Materials in Shear Flow ;210
4.6.2.1;2.1. Experiments;210
4.6.2.2;2.2. Theories;217
4.6.3;3. Spatio-temporal Rheological Oscillations and Chaotic Dynamics 3.1. Theoretical Investigations of Spatio- temporal Rheochaos;225
4.6.4;4. Proposed Experiments;233
4.6.5;Acknowledgments;233
4.6.6;References;234
4.7;Chapter 7 WETTING OF FIBERS;238
4.7.1;1. Introduction;238
4.7.2;2. The Rayleigh-Plateau Instability;239
4.7.3;3. Drop Shapes;240
4.7.3.1;3.1. Axisymmetric Shapes;241
4.7.3.2;3.2. Asymmetric Droplets;242
4.7.4;4. Heterogeneous Fiber;245
4.7.5;5. Invasion of a Network of Fibers;246
4.7.6;6. Conclusions and Perspectives for the Future;251
4.7.7;References;251
5;TECHNIQUES;254
5.1;Chapter 8 GEL FORMATION: PHASE DIAGRAMS USING TABLETOP RHEOLOGYAND CALORIMETRY;256
5.1.1;1. Introduction;256
5.1.2;2. Detecting the Sol-Gel Transition by Tabletop Rheology;257
5.1.2.1;2.1. Tube Inversion;258
5.1.2.2;2.2. Falling of Spheres;260
5.1.2.3;2.3. Rise of Bubbles;261
5.1.2.4;2.4. Other Methods;261
5.1.3;3. Thermodynamics of Gelation: Sol-Gel Transition by Calorimetry;262
5.1.3.1;3.1. First- and Second-Order Phase Transitions;263
5.1.3.2;3.2. The Question of Gelation;263
5.1.3.3;3.3. Calorimetry of the Sol-Gel Transition;265
5.1.3.4;3.4. Gelation Temperature vs. Gelator Concentration;265
5.1.4;4. Conclusions and Perspectives;266
5.1.5;References;267
5.2;Chapter 9 DIRECT- IMAGINGAND FREEZE-FRACTURE CRYO- TRANSMISSION ELECTRON MICROSCOPY OF MOLECULAR GELS;268
5.2.1;1. Introduction;268
5.2.2;2. Cryo-TEM;269
5.2.3;3. Cryo-TEM Investigations of LMOG Gels;273
5.2.4;4. Conclusions and Perspectives for the Future;286
5.2.5;References;286
5.3;Chapter 10 MOLECULAR GELS AND SMALL-ANGLE SCATTERING;290
5.3.1;1. Foreword;291
5.3.2;2. Introduction;291
5.3.3;3. Basic Principles;294
5.3.4;4. Form-Factors of Rod-Like Scatterers;297
5.3.4.1;4.1. Plain Fibers;297
5.3.4.2;4.2. Short Rods;305
5.3.5;5. Semi-Rigid Fibers;307
5.3.6;6. Fibers with Anisometric Sections;308
5.3.6.1;6.1. Rectangular Sections;309
5.3.6.2;6.2. Elliptical Cross-Sections;309
5.3.7;7. Tubes;310
5.3.8;8. Helices;313
5.3.9;9. Scattering by the Junction Zones;315
5.3.9.1;9.1. Form-Factor of a Disk;315
5.3.9.2;9.2. Spherulitic Nodes;317
5.3.9.3;9.3. Random Nodes: Debye-Büeche Context;317
5.3.9.4;9.4. Ideally Homogeneous Networks;318
5.3.9.5;9.5. Fractal Context;319
5.3.9.6;9.6. Orientation Correlated Domains;320
5.3.10;10. Structure Factor Peak in Poorly Organized Fibrillar Scatterers;322
5.3.11;11. Oriented Fibers;326
5.3.11.1;11.2. Shear Alignment;327
5.3.12;12. Real Space Data;331
5.3.13;13. Kinetic Studies;332
5.3.14;14. Useful Hints for a Standard SANS Investigation of Molecular Gels;334
5.3.15;15. Conclusions;336
5.3.16;References;337
5.4;Chapter 11 X- RAYDIFFRACTION OF POORLYORGANIZED SYSTEMS AND MOLECULAR GELS;340
5.4.1;1. Introduction;340
5.4.2;2. Long Range Ordering;342
5.4.2.1;2.1. Diffraction and Diffuse Scattering;342
5.4.2.2;2.2. The Crystal Structure;342
5.4.3;3. Single Crystal Diffraction;344
5.4.3.1;3.1. The Structure Factor;345
5.4.3.2;3.2. Crystal Structure Solution;346
5.4.4;4. Powder Diffraction;352
5.4.4.1;4.1. Structure Determination from Powders;353
5.4.4.2;4.2. Multi-phases and Quantification by Profile Refinement Techniques;359
5.4.5;4.3. Microstructures;360
5.4.6;5. X-Rays and Neutrons;362
5.4.7;6. Applications of Diffraction;363
5.4.7.1;6.1. Partially Disordered Compounds: Pharmaceutical Molecules;363
5.4.7.2;6.2. Molecular Gels;368
5.4.8;7. Conclusions;375
5.4.9;References;376
5.5;Chapter 12 OPTICAL SPECTROSCOPIC METHODS AS TOOLS TO INVESTIGATE GEL STRUCTURES;378
5.5.1;1. Introduction;378
5.5.2;2. Electronic Absorption and Emission Spectroscopy 2.1. General Considerations Concerning UV- vis and Fluorescence Spectroscopy;379
5.5.3;3. Infrared Spectroscopy;422
5.5.3.1;3.1. General Considerations;422
5.5.3.2;3.2. Selected Examples Illustrating the Application of Infrared Spectroscopy to the Study of Gel Structures;424
5.5.3.3;3.3. IR Absorption Spectroscopy of 2,3-Di-n-decyloxyanthracene (DDOA). Assignment of Vibration Bands and Dichroic Absorption;434
5.5.4;4. Conclusions and Perspectives for the Future;440
5.5.5;References;440
5.6;Chapter 13 CIRCULAR DICHROISM FOR STUDYING GEL- LIKE PHASES;446
5.6.1;1. Introduction;446
5.6.2;2. Technique;447
5.6.2.1;2.1. How to Obtain CD Spectra;448
5.6.2.2;2.2. Experimental Problems;449
5.6.3;3. Applications to the Study of Gel-Like Phases;450
5.6.4;4. Conclusions and Perspectives for the Future;460
5.6.5;References;460
6;SYSTEMS – ORGANOGELS;463
6.1;Chapter 14 LOW MOLECULAR-MASS ORGANIC GELATORS;464
6.1.1;1. Introduction;464
6.1.2;2. Classification of Organic Gelators;465
6.1.2.1;2.1. Alkane Gelators;466
6.1.2.2;2.2. Organic Gelators with One Heteroatom;466
6.1.2.3;2.3. Organic Gelators with Two Heteroatoms;485
6.1.2.4;2.4. Organic Gelators Containing Three Heteroatom Types;513
6.1.2.5;2.5. Polymerizable Organic Gelators;515
6.1.2.6;2.6. Two Component Organic Gelators;518
6.1.2.7;2.7. Inorganic and Organometallic Gelators;528
6.1.2.8;2.8. Liquid-Crystalline Gels;529
6.1.2.9;2.9. Latent Gelators;534
6.1.2.10;2.10. Microemulsion-based Gelators;536
6.1.2.11;2.11. Miscellaneous Organic Gelators;538
6.1.3;3. The Role of Liquid in Gelation by LMOGs;542
6.1.4;4. Conclusions and Perspectives for the Future;550
6.1.5;Acknowledgments;552
6.1.6;References;552
6.2;Chapter 15 DESIGN AND FUNCTION OF LOW MOLECULAR- MASS ORGANIC GELATORS ( LMOGs) BEARING STEROID AND SUGAR GROUPS;568
6.2.1;1. Introduction;568
6.2.2;2. Steroid Derivatives for Gelating Organic Liquids ;569
6.2.2.1;2.1. Introduction;569
6.2.2.2;2.2. Structural Variations of Steroid-Based Gelators and their Analyses;569
6.2.2.3;2.3. Functional Applications of Cholesterol-Based LMOGs;572
6.2.2.4;2.4. Conclusions;578
6.2.3;3. Sugar Derivatives for Gelating Liquids;579
6.2.3.1;3.1. Introduction;579
6.2.3.2;3.2. Structural Variations of Sugar-Based Gelators;579
6.2.3.3;3.3. Dual-Component Gelators Based on Charge-Transfer Phenomena;582
6.2.3.4;3.4. Combinatorial Approaches for Finding Gelators and Building Integrated Systems Utilizing a Sugar Library;582
6.2.3.5;3.5. Conclusions;584
6.2.4;4. Other Related LMOGs ;585
6.2.4.1;4.1. Nucleobase Gelators;585
6.2.4.2;4.2. Vancomycin Gelator;588
6.2.5;5. Perspectives for the Future;589
6.2.6;References;589
6.3;Chapter 16 SAFIN GELS WITHAMPHIPHILIC MOLECULES;592
6.3.1;1. Introduction;592
6.3.2;2. Amphiphilic Molecules ;593
6.3.2.1;2.1. Amphiphilicity;593
6.3.2.2;2.2. Amphiphilic Molecules;593
6.3.3;3. Gels with Amphiphilic Molecules;596
6.3.3.1;3.1. Characteristics of SAFIN Gels with Amphiphilic Molecules;597
6.3.3.2;3.2. Amphiphilic Molecules which Form SAFIN Gels;599
6.3.3.3;3.3. Chiral Supramolecular Structures;603
6.3.4;4. Gemini Amphiphilic Molecules ;606
6.3.4.1;4.1. Definitions;606
6.3.4.2;4.2. Particularities of Gemini Molecules;607
6.3.4.3;4.3. What Kind of Gemini Molecules Form Gels?;608
6.3.5;5. Conclusions and Perspectives for the Future;614
6.3.6;Acknowledgment;616
6.3.7;References;617
7;SYSTEMS – HYDROGELS;626
7.1;Chapter 17 ADVANCES IN MOLECULAR HYDROGELS;628
7.1.1;1. Introduction;628
7.1.2;2. Historical Perspectives;630
7.1.3;3. Amino Acid and Oligopeptide Based Hydrogelators;631
7.1.4;4. ß-Peptide Based Hydrogelators;640
7.1.5;5. Carbohydrate Based Gelators;643
7.1.6;6. Hydrogelators from Bola-amphiphiles and Gemini Surfactants;646
7.1.7;7. Miscellaneous Hydrogelators;649
7.1.8;8. Bile Acid Based Hydrogelators;651
7.1.9;9. Structural and Dynamic Aspects of Hydrogels;655
7.1.10;10. Application of Hydrogels in Materials Science;657
7.1.11;11. Perspectives for the Future;658
7.1.12;Abbreviations;659
7.1.13;Acknowledgments;659
7.1.14;References;659
7.2;Chapter 18 AQUEOUS GELS MADE OF CHIRAL LIPID- AND PORPHYRIN- AMPHIPHILES;664
7.2.1;1. Introduction;664
7.2.2;2. Electron Microscopy in Water and Toluene;664
7.2.3;3. The Effect of Charge Repulsion in Water;666
7.2.4;4. Stereochemistry and the Chiral Bilayer Effect;668
7.2.5;5. Viscoelastic Gels inWater;675
7.2.6;6. Bolaamphiphiles;676
7.2.7;7. Conclusions;676
7.2.8;References;678
8;ANALYSES OF SPECIFIC SYSTEMS;681
8.1;Chapter 19 RHEOLOGY OF WORMLIKE MICELLES: EQUILIBRIUM PROPERTIES AND SHEAR BANDING TRANSITIONS;682
8.1.1;1. Introduction;682
8.1.2;2. Equilibrium Properties;684
8.1.2.1;2.1. Theoretical Background;684
8.1.2.2;2.2. Physical Chemistry ofWormlike Micelles and Related Systems;685
8.1.2.3;2.3. Flexibility ofWormlike Micelles;689
8.1.2.4;2.4. Phase Behavior;693
8.1.2.5;2.5. Linear Rheology and Scaling;695
8.1.2.6;2.6. Concluding Remarks on the Equilibrium Properties;700
8.1.3;3. Shear Banding Transition in Concentrated and Semi- Dilute Regimes;701
8.1.3.1;3.1. Isotropic-to-Nematic Transition in the Concentrated Regime;702
8.1.3.2;3.2. Shear Banding in Semi-Dilute Regime;711
8.1.3.3;3.3. Theories and Interpretations;717
8.1.4;4. Conclusions and Perspectives for the Future;721
8.1.5;Acknowledgments;722
8.1.6;References;723
8.2;Chapter 20 CRYO- TEM, X-RAY DIFFRACTION AND MODELING OFAN ORGANIC HYDROGEL;736
8.2.1;1. Introduction;736
8.2.2;2. Techniques;737
8.2.3;3. Modeling Gel Structure;738
8.2.3.1;3.1. Molecular Structure;739
8.2.3.2;3.2. Nanometer Structure;739
8.2.3.3;3.3. Micrometer Structure;743
8.2.4;4. A Case Study;744
8.2.4.1;4.1. Cryo-Transmission Electron Microscopy;746
8.2.4.2;4.2. X-ray Diffraction;747
8.2.4.3;4.3. Modeling;749
8.2.5;5. Perspectives for the Future;752
8.2.6;Acknowledgments;753
8.2.7;References;753
8.3;Chapter 21GELATION OFA LIQUID-CRYSTALLINE La PHASE INDUCED BY THE PROLIFERATION OF TOPOLOGICAL DEFECTS;758
8.3.1;1. Introduction;759
8.3.1.1;1.1. Basic De.nitions;759
8.3.1.2;1.2. Topological Defects in an Organized Phase Can Induce Gelation;762
8.3.1.3;1.3. Scope and Outline of the Chapter;762
8.3.2;2. Gelation of a Lamellar La Phase by Additionof Peg-Lipids;763
8.3.2.1;2.1. Description of the System and its Components;763
8.3.2.2;2.2. Phase Diagram and Gelation;764
8.3.2.3;2.3. Observations of Samples in Polarized Light;766
8.3.2.4;2.4. Electron Microscopy;767
8.3.2.5;2.5. X-Ray Scattering;768
8.3.2.6;2.6. Rheology;770
8.3.2.7;2.7. Model and Discussion;772
8.3.3;3. A New Class of Gels;774
8.3.3.1;3.1. Extensive Chemical Modi.cation of PEG-lipids Does not Affect Their Gelating Power;774
8.3.3.2;3.2. Double-End-Anchored PEG-Surfactants also Induce Gelation;776
8.3.4;4. Generalization;780
8.3.4.1;4.1. Gelation of a Lamellar Phase by Addition of Particles;780
8.3.4.2;4.2. Gelation of Other Mesophases;780
8.3.4.3;4.3. Ringing Gels ;781
8.3.5;5. Conclusions and Perspectives for the Future;782
8.3.6;Acknowledgments;782
8.3.7;References;782
9;APPLICATIONS;786
9.1;Chapter 22 GELS OF LIQUID CRYSTALS AND ION- CONDUCTING FLUIDS;788
9.1.1;1. Introduction;788
9.1.2;2. Liquid Crystal and Ion Conducting Gels for Electro Optical Devices;789
9.1.2.1;2.1. Gels with Chemically Cross-Linked Networks;789
9.1.2.2;2.2. Photopolymerization of Acrylates;789
9.1.2.3;2.3. Liquid Crystal Gels;790
9.1.2.4;2.4. Ion Conducting Gels;796
9.1.3;References;806
9.2;Chapter 23 ELECTRON CONDUCTINGAND MAGNETO- SENSITIVE GELS;808
9.2.1;1. Introduction;808
9.2.1.1;1.1. Electron Conduction in Conducting Polymers;809
9.2.1.2;1.2. Conducting Gels;813
9.2.2;2. Molecular Gels as Templating Media for Electronic Materials;820
9.2.2.1;2.1. Polymerizable LMOGs;821
9.2.2.2;2.2. Templating of Inorganic Structures;821
9.2.2.3;2.3. Spatial Organization of Semiconductor Nanoparticles;823
9.2.3;3. Magnetosensitive Gels;823
9.2.4;4. Conclusions and Perspectives for the Future;825
9.2.5;Acknowledgments;825
9.2.6;References;825
9.3;Chapter 24 PHOTORESPONSIVE GELS;832
9.3.1;1. Luminescent Gels;832
9.3.1.1;1.1. General Considerations;832
9.3.1.2;1.2. Luminescent Organogels and Energy Transfer;839
9.3.2;2. Phototunable Gels;850
9.3.2.1;2.1. General Considerations;851
9.3.2.2;2.2. Systems;852
9.3.2.3;2.3. Photochromic Gels Based on Polymers;856
9.3.2.4;2.4. Photochromic Properties Modulated by the Sol-Gel Transitions Using LMOGs;858
9.3.2.5;2.5. Irreversible, Photo-Induced Phase Transitions Using LMOGs;859
9.3.2.6;2.6. Reversible, Photo-Induced Phase Transitions Using LMOGs;861
9.3.3;3. Conclusions and Perspectives for the Future;865
9.3.4;Acknowledgments;866
9.3.5;References;866
9.4;Chapter 25 GELS OF LOW MOLECULAR-MASS ORGANIC GELATORS AS TEMPLATES FOR TRANSCRIPTION;872
9.4.1;1. Introduction;873
9.4.2;2. The Basics of Sol-Gel Chemistry;875
9.4.2.1;2.1. Hydrolysis;877
9.4.2.2;2.2. Condensation;878
9.4.3;3. Transcription of the Gelator Template;879
9.4.3.1;3.1. Gelators Possessing Covalently Attached, Positively Charged Centers;880
9.4.3.2;3.2. Gelators Containing Non-Covalently Attached, Positively Charged Centers;883
9.4.3.3;3.3. Gelators Containing Hydrogen-Bond Donating Amine Groups;885
9.4.3.4;3.4. Gelators with Different Structural Features;887
9.4.3.5;3.5. Outlook for the Future;889
9.4.4;4. Shapes of Transcribed Materials;890
9.4.4.1;4.1. Transcription of Cholesterol-Based Gelators;892
9.4.4.2;4.2. Transcription of Sugar-Based Gelators;897
9.4.4.3;4.3. Transcription of Cyclohexane-Based Gelators;901
9.4.4.4;4.4. Perspectives for the Future;903
9.4.5;5. General Conclusions and Challenges for the Future;903
9.4.6;References;905
9.5;Chapter 26 RESPONSIVE MOLECULAR GELS;910
9.5.1;1. Introduction;910
9.5.1.1;1.1. Responsive Chemical Gels;911
9.5.1.2;1.2. Responsive Physical Gels;912
9.5.1.3;1.3. Triggering Signals and Expected Responses;912
9.5.1.4;1.4. Boundaries and Limitations;914
9.5.2;2. Chemo-Responsive Gels;914
9.5.2.1;2.1. Chemo-Responsive Gels by Host-Guest Complexation;915
9.5.2.2;2.2. Metal-Ion Responsive Gels;920
9.5.2.3;2.3. Responsive Gel Systems by Uptake and Release of Gasses;922
9.5.2.4;2.4. Gel-Sol Phase Transitions Triggered by pH Changes;923
9.5.3;3. Physico-Responsive Gels;929
9.5.3.1;3.1. An Unusual Temperature Responsive LMOG Gel;929
9.5.3.2;3.2. Reponses to Mechanical Stress;930
9.5.3.3;3.3. Light-Responsive Gels;932
9.5.4;4. Conclusions and Perspectives for the Future;939
9.5.5;References;940
9.6;Chapter 27 GELS AS CLEANING AGENTS IN CULTURAL HERITAGE CONSERVATION;944
9.6.1;1. Introduction;944
9.6.2;2. Polyacrylic Acid-Based Gels in Cultural Heritage Conservation;948
9.6.3;3. Application and Removal of Gels from Painted Surfaces;949
9.6.4;4. Future Perspectives;951
9.6.5;References;951
10;COLOR SECTION;955
11;INDEX;964