لایب سان

1 Introduction Peter A. Williams 1 1.1 Rheological behaviour 1 1.2 Polymer adsorption and colloid stability 2 1.3 Surface modification 6 1.4 Complexation and controlled release 7 1.5 Packaging 8 References 8 2 Natural Thickeners Graham Sworn 10 2.1 Introduction 10 2.1.1 Marine polysaccharides 10 2.1.2 Botanical polysaccharides 13 2.1.3 Microbial polysaccharides 14 2.1.4 Chemically modified polysaccharides 14 2.2 Introduction to rheology 15 2.2.1 Measurement of viscosity 16 2.2.2 Measurement of viscoelasticity 17 2.3 Rheology of natural thickeners 18 2.3.1 Viscosity of entanglement network solutions 19 2.3.2 Viscoelasticity of entanglement network solutions 22 2.3.3 Weak and strong gels 23 2.4 Dispersion and hydration 25 2.5 Food applications of natural thickeners 26 2.5.1 Dressings and sauces 26 2.5.2 Beverages 26 2.5.3 Baking 27 2.5.4 Ice cream 27 2.6 Non-food applications 27 2.6.1 Oil drilling fluids 28 2.6.2 Acidic, basic and chlorinated cleaning products 28 2.6.3 Personal care and cosmetics 29 2.6.4 Textile printing 29 2.6.5 Paper coating 30 2.6.6 Building materials 30 2.7 Conclusions 30 References 30 3 Acrylic Polymers as Rheology Modifiers for Water-Based Systems Malcolm Hawe 32 3.1 Introduction 32 3.2 Chemistry of acrylic polymer thickeners 33 3.2.1 Addition polymers 33 3.3 Polymer synthesis techniques 38 3.3.1 Polymer physical forms 39 3.3.2 Liquid grades 40 3.4 Polymer characterisation 44 3.4.1 Polymer characterisation techniques 44 3.4.2 Rotational viscometers 49 3.5 Basic concepts of rheological behaviour 51 3.5.1 Advances in rheological characterisation 53 3.5.2 Extensional viscosity 60 3.6 End-use applications for synthetic thickeners 62 3.6.1 Oilfield flooding applications 62 3.6.2 Drag reduction 63 3.6.3 Textile printing applications 64 3.6.4 Emulsion paints and water-based coatings 66 3.6.5 Cosmetic, toiletry and household formulations 67 3.6.6 Agricultural spray systems 68 3.7 Conclusion 69 Acknowledgements 69 Appendix 70 References 70 4 Gelling Agents Peter A. Williams 73 4.1 Introduction 73 4.2 Gelation triggered by temperature 76 4.2.1 Gels formed on cooling 76 4.2.2 Gel formation on heating 84 4.3 Ion-mediated gelation 85 4.3.1 Cation-mediated gelation 85 4.3.2 Anion-mediated gelation 89 4.4 Retrogradation 91 4.4.1 Starch 91 4.4.2 Konjac mannan 94 4.5 Summary 95 References 95 vi Contents 5 Emulsification and Encapsulation D. Julian McClements 98 5.1 Introduction 98 5.2 Emulsions 98 5.2.1 Introduction 98 5.2.2 Droplet characteristics 100 5.2.3 Formation of emulsions 104 5.2.4 Encapsulation of emulsified lipids 105 5.2.5 Emulsion stability 107 5.2.6 Bulk physicochemical properties of emulsions 111 5.3 Water soluble polymer emulsifiers 114 5.3.1 Introduction 114 5.3.2 Molecular characteristics 114 5.3.3 Interfacial activity and emulsion stabilization 115 5.4 Selection of an appropriate polymeric emulsifier 119 5.5 Common water soluble polymers used as emulsifiers in foods 121 5.5.1 Proteins 121 5.5.2 Polysaccharides 125 5.5.3 Protein–polysaccharide complexes 127 5.6 Conclusions 128 References 128 6 Polymeric Flocculants Gillian M. Moody 134 6.1 Introduction 134 6.2 Basic theory of suspensions and flocculation 134 6.2.1 The mechanism of bridging flocculation 135 6.2.2 The charge patch mechanism 137 6.3 Material types 138 6.3.1 Natural products 138 6.3.2 Synthetic polymers 139 6.4 Synthesis of synthetic water soluble polymers 140 6.5 Characterisation of industrial water soluble polymers 145 6.5.1 Ionic character 145 6.5.2 Viscosity 146 6.5.3 Molar mass 146 6.6 Solid/liquid separation 148 6.6.1 Clarifiers 150 6.6.2 Thickeners 150 6.6.3 Centrifuges 151 6.6.4 Filters 151 6.6.5 Flocculant selection 153 6.6.6 Coagulant use 153 6.6.7 Operating strategies 153 6.7 Mineral processing 154 6.8 Oil industry applications 156 6.8.1 Water injection systems 156 6.8.2 Oily water clarification 156 Contents vii 6.9 Municipal wastewaters and sludges 157 6.10 Industrial effluents 161 6.11 Potable water treatment 163 6.12 Paper making applications 163 6.12.1 Retention, drainage and formation 163 6.12.2 Flocculation mechanisms in paper making 164 6.12.3 Development of retention, drainage and formation programs 165 6.13 The use of high molecular weight flocculants in agriculture 168 6.14 Conclusions 169 Acknowledgments 170 References 170 7 Polymer Micelles: Amphiphilic Block and Graft Copolymers as Polymeric Surfactants Gérard Riess 174 Nomenclature 174 7.1 Introduction 176 7.2 Structures and synthesis of block and graft copolymers 177 7.2.1 Block copolymers with linear A-B and A-B-A architecture 178 7.2.2 Block copolymers with complex molecular architecture 183 7.2.3 Graft copolymers 184 7.3 Block and graft copolymer micelles in aqueous medium 189 7.3.1 Generalities 189 7.3.2 Preparation techniques 191 7.3.3 Characterization of copolymer micelles: experimental techniques 191 7.3.4 Dynamics of micellar systems 194 7.3.5 Solubilization in micelles 195 7.3.6 Thermodynamic aspects, theories and computer simulations 196 7.3.7 Micellization of non-ionic amphiphilic block copolymers 197 7.3.8 Micellization of anionic amphiphilic copolymers 201 7.3.9 Micellization of cationic amphiphilic copolymers 202 7.3.10 Micellization of double-hydrophilic copolymers 204 7.3.11 Cross-linked micellar structures 207 7.3.12 Micellization of copolymers with complex molecular architecture 208 7.3.13 Comicellization and complex formation 212 7.4 Application possibilities of biocompatible copolymer micellar systems 215 7.4.1 Solubilization of bioactive components in micellar systems: controlled drug release 215 7.4.2 Miscellaneous biomedical applications 219 7.5 Conclusions 220 Acknowledgments 221 References 221 viii Contents 8 Applications of Water-Soluble Dendrimers Philip Woodward, Steven Rannard and Wayne Hayes 239 8.1 Introduction 239 8.2 Medical applications of dendrimers 243 8.2.1 Dendritic drug delivery systems 243 8.2.2 Dendrimer mediated gene transfection 247 8.2.3 Dendritic medical imaging systems 248 8.2.4 Other medical applications of dendrimers 250 8.3 Dendritic metal nanoparticles 252 8.4 Dendritic catalysts 254 8.5 Dendritic phase transfer catalysts 255 8.6 Dendritic sensor and indicator devices 256 8.7 Dendrimer surfactants 256 8.8 Dendritic coatings 259 8.9 Selective dendritic complexation agents for heavy metal ions 259 8.10 Dendritic porogenic agents 260 8.11 Hydrogels/gelators 261 8.12 Other notable applications of water-soluble dendrimers 262 8.13 Conclusion 264 References 264 9 Preparation, Properties and Applications of Colloidal Microgels Louise H. Gracia and Martin J. Snowden 268 9.1 Introduction 268 9.2 Microgel preparation 269 9.2.1 Emulsion polymerisation 269 9.2.2 Inverse EP 271 9.2.3 Living free-radical polymerisation 272 9.2.4 Radiation polymerisation 273 9.2.5 Synthesis of core-shell microgels 273 9.3 Characterisation of microgels 274 9.3.1 Dynamic light scattering 274 9.3.2 Small-angle neutron scattering 275 9.3.3 Turbidimetric analysis 276 9.3.4 Other techniques 277 9.4 Properties and applications 278 9.4.1 Thermosensitive microgels 278 9.4.2 Effects of co-monomers 281 9.4.3 pH sensitivity 282 9.4.4 Swelling and de-swelling behaviour 283 9.4.5 Effects of cross-linkers 284 9.4.6 Osmotic de-swelling 284 9.4.7 Colloid stability 285 9.4.8 Microgel structure 287 9.4.9 Rheological properties 288 Contents ix 9.4.10 Electrical properties 290 9.4.11 Drug delivery vehicles 290 9.4.12 Other current areas of applications 293 9.5 Conclusions 294 References 295 10 Industrial Water Soluble Polymers in Packaging Radek Messias de Bragança and Paul A. Fowler 298 10.1 Introduction 298 10.2 Present-day challenges to IWSPs for packaging 298 10.2.1 Renewability paradigm, or predicted exhaustion of world petroleum reserves and global warming challenge 298 10.2.2 Need to ensure biodegradability in packaging materials 300 10.3 Survey of IWSPs used in packaging 301 10.3.1 Synthetic IWSPs 302 10.3.2 Naturally derived IWSPs 305 10.3.3 Conclusions 317 10.4 Key characteristics of materials used in packaging 318 10.4.1 Barrier properties 318 10.4.2 Thermal and mechanical properties 320 10.4.3 Ageing of polymers 320 10.4.4 Manipulation of critical barrier/thermo-mechanical properties 320 10.5 Conclusion 321 References 322 Index 325

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