Gel Chemistry (eBook)

Jianyong Zhang received his PhD in Chemistry from the National University of Singapore in 2003 after obtaining a B.Sc. from Central South University of Technology, China in 1996 and an MSc from Nankai University, China in 1999. He was a post-doctoral research fellow at the Institut de Recherches sur la Catalyse (CNRS), France from 2002 to 2003 and at Queen’s University Belfast from 2003 to 2006. He joined Sun Yat-Sen University, China where he currently serves as a professor at the School of Materials Science and Engineering, in 2006. His research interests and activities are mainly in the interdisciplinary areas of supramolecular chemistry, materials chemistry, catalysis, and organometallic/coordination chemistry. His recent work primarily focuses on dynamic covalent gels, metal-organic gels and coordination-based supramolecular materials.

Contents 6
1 Introduction 9
Abstract 9
1.1 Components of Gels 9
1.2 Driving Force 11
1.3 Characterization 12
References 14
2 Supramolecular Gels 16
Abstract 16
2.1 Heat/Temperature Responsive Gels 17
2.2 Light Responsive Gels 23
2.2.1 Conformational Changes 23
2.2.1.1 Azobenzenes 25
2.2.1.2 Stilbenes 27
2.2.2 Coupling Reactions 29
2.2.2.1 Diacetylenes 29
2.2.3 Electrocyclic Reactions 30
2.2.3.1 Spiropyrans and Spirooxazines 31
2.2.3.2 Dithienylethenes 32
2.3 Sonication and Mechanical Stress Responsive Gels 36
2.3.1 Ultrasound 37
2.3.2 Mechanical Stress 41
2.4 Chemical Responsive Gels 44
2.4.1 Acid and Base 44
2.4.2 Redox 47
2.4.3 Ion 49
2.4.4 Neutral Species 55
2.5 Conclusions 58
References 59
3 Metal–Organic Gels 67
Abstract 67
3.1 Discrete Gelators 68
3.1.1 Metal–Organic Gelators with Monodentate Ligands 68
3.1.2 Metal–Organic Gelators with Chelate Ligands 71
3.1.3 Organometallic Gelators 76
3.1.4 Metal–Organic Gelators Based on Tripyridine and Tridentate Ligands 78
3.1.5 Coordination Cages 82
3.2 Coordination Polymer Gelators 87
3.2.1 Metal-Carboxylate Gels 87
3.2.2 Metal-Heterocycle Polymer Gels 95
3.2.3 Coordination Polymer Gels with Hybrid Donors 101
3.3 Applications 107
3.3.1 Gels as Crystallization Media 107
3.3.2 Post-modification of Organogels by Metal Ions 109
3.3.3 Metal–Organic Gels for Sorption 111
3.3.4 Metal–Organic Gels as Template 112
3.3.5 Metal–Organic Gels as Catalyst 114
References 117
4 Dynamic Covalent Gels 125
Abstract 125
4.1 Discrete Gelators 127
4.1.1 Imine/Acylhydrazone Gels 127
4.1.2 Imine/Acylhydrazone Gels and Metal Ions 134
4.1.3 Borate Gels 141
4.1.4 Conversions Between Anthracene and Its Dimer 145
4.1.5 Dynamic Covalent Cycles and Cages 145
4.2 Dynamic Covalent Polymer Gelators 147
4.2.1 Imine Gels 149
4.2.2 Calix[4]Arene-Derived Acylhydrazone Gels 151
References 154
5 Polymer Gels 158
Abstract 158
5.1 Introduction to Polymer Gels 158
5.1.1 Cross-Linking of Polymer Chains 159
5.1.2 Traditional Polymer Gels 160
5.2 Fundamental Aspects 162
5.2.1 Concepts 162
5.2.2 Mechanical Properties 163
5.2.3 Swelling and Shrinking Properties 163
5.3 Nature of Cross-Linking Leading to the Formation of Polymer Gels 167
5.3.1 Hydrogen-Bonded Polymer Gels 167
5.3.2 Metal–Organic Coordination Polymer Gels 170
5.3.3 Polymer Gels Based on Dynamic Covalent Chemistry 176
5.3.4 Hybrid Polymer and Low Molecular Weight Gels 183
References 190
6 Inorganic Gels 195
Abstract 195
6.1 Sol–Gel Process for Gel Formation 196
6.2 Silica-Based Gels 198
6.3 Chalcogels 203
6.4 Other Inorganic Gels 208
References 210
Index 213