Presenting a unique perspective on state-of-the-art physical gels, this interdisciplinary guide provides a complete, critical analysis of the field and highlights recent developments. It shows the interconnections between the key aspects of gels, from molecules and structure through to rheological and functional properties, with each chapter focusing on a different class of gel. There is also a final chapter covering innovative systems and applications, providing the information needed to understand current and future practical applications of gels in the pharmaceutical, agricultural, cosmetic, chemical and food industries. Many research teams are involved in the field of gels, including theoreticians, experimentalists and chemical engineers, but this interdisciplinary book collates and rationalises the many different points of view to provide a clear understanding of these complex systems for researchers and graduate students.

Preface ix

1 Introduction 1

1.1 Gels from colloidal and polymer networks: a brief survey 1

1.2 Structural characteri stics and their study 3

1.3 Non-physical gels 6

1.4 Physical gels 8

1.5 Outline of the book 12

References 16

Bibliography 17

2 Techniques for the characterization of physical gels 18

2.1 Introduction 18

2.2 Scattering techniques 18

2.3 Calorimetric studies 26

2.4 Microscopy of gel networks 33

2.5 Rheological characterization 40

2.6 Role of numerical simulations 52

2.7 Conclusions 61

References 61

3 The sol-gel transition 64

3.1 Flory-Stockmayer （‘classical’） theory 64

3.2 Percolation model 66

3.3 Percolation and phase transitions 72

3.4 Percolation and gelation 75

3.5 Experimenta l investigations of gelation transitions 80

3.6 Eldridge←Ferry method 87

3.7 Critical gel concentration 88

3.8 Zipper model 90

3.9 Liquid crystal gels 91

3.10 Conclusions 93

References 94

4 General properties of polymer networks 97

4.1 Chemically cross-linked networks and gels 98

4.2 Theories of rubber elasticity 102

4.3 Swelling of gels 104

4.4 Transient networks 109

4.5 Conclusions 122

References 122

5. Ionic gels 124

5.1 Introduction 124

5.2 Molecular characteristics of polyelectrolytes 125

5.3 Polyelectrolyte theories 126

5.4 Gelai-ion of carrageenans and gellans 127

5.5 Gelation of alginates and pectins 144

5.6 Xanthan 149

5.7 Chitin and cbitosan 151

5.8 Conchusions 152

References 152

6 Hydrophobically associated networks 156

6.1 Introduction 156

6.2 The hydrophobic effect 156

6.3 Hydrophobically rnodi_fied water-soluble polymers 161

6.4 Rheology of associating polym ers 167

6.5 Interaction with surfactants 170

6.6 Therrnogelation or phase separation ? 173

6.7 Conclusions 180

References 180

7 Helical structures from neutral biopolymers 182

7.1 Introduction 182

7.2 Gelatin 182

7.3 Agarose 208

7.4 Comparison between helical type networks 2 17

7.5 Conclusions 219

References 220

8 Gelation through phase transfornation in synthetic and natural polymers 222

8.1 Introduction 222

8.2 ‘Crystallization ’ induced gelation: poly(vinylchloride) (PVC) gels 223

8.3 Gelation in the absence of crystallization 230

8.4 Stereo-complexation and conformational changes: isotactic and syndiotactic PMMA gels

239

8.5 Cryogels of poly(vinyl alcohol) (PVA) 245

8.6 Cryogels from polysaccharides 251

8.7 Conclusions 253

References 254

9 Colloidal gels from proteins and peptides

9.1 Introduction

9.2 Colloidal gels fonned from partially denatured proteins

9.3 Gels from milk proteins

9.4 Fibrillar gels formed from partially denatured proteins

9.5 Specific assemblies from peptides and proteins

9.6 Conclusions References

10 Mixed gels 287

10.1 Introduction 287

10.2 Equilibrium thermodynamic s 289

10.3 Phase dynamics: nucleation and growth versus spinodal decomposition 290

10.4 Gels involving segregative phase separation 298

10.5 Filled gels 309

10.6 Gels involving molecular ('synergistic’） interactions 3 l O

10.7 Conclusion s 322

References 322

11 Innovative systems and applications 326

11.1 Innovative systems 326

11.2 Food and cosmetic applications 334

11.3 Biomedical applications 336

11.4 Conclusions 351

References 351

index 353

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