Surfactant Science and Technology

DREW MYERS obtained his Ph.D. in Organic Chemistry with secondary specialization in Medicinal Chemistry at the University of Utah in 1974 and his M.Sc. in Surface and Colloid Science at the University of Bristol in 1979. He has been a consultant in surface, colloid, organic, and polymer chemistry since 1986.

Preface xv

1 An Overview of Surfactant Science and Technology 1

1.1 A Brief History of Surfactant Science and Technology 3

1.2 Surfactants in the Modern World 5

1.3 The Economics of Surfactant Science and Technology 8

1.4 The Near-Term Economic and Technological Future for Surfactants 10

1.5 Surfactantsin the Environment 11

1.6 A Surfactant Glossary 13

2 The Classification of Surfactants 17

2.1 The Basic Structure of Amphiphilic Molecules 17

2.2 A Systematic Classification of Surfactants 19

2.2.1 Surfactant Solubilizing Groups 19

2.2.2 Making a Choice 21

2.3 The Generic Anatomy of Surfactants 21

2.3.1 The Many Faces of Dodecane 22

2.3.2 Surfactant Solubilizing Groups 25

2.3.3 Common Surfactant Hydrophobic Groups 26

2.3.3.1 The Natural Fatty Acids 27

2.3.3.2 Saturated Hydrocarbons or Paraffins 28

2.3.3.3 Olefins 28

2.3.3.4 Alkyl Benzenes 29

2.3.3.5 Alcohols 29

2.3.3.6 Alkyl Phenols 30

2.3.3.7 Polyoxypropylenes 30

2.3.3.8 Fluorocarbons 31

2.3.3.9 Silicone Surfactants 32

2.3.3.10 Miscellaneous Biological Structures 32

2.4 The Systematic Classification of Surfactants 33

2.5 Anionic Surfactants 34

2.5.1 Sulfate Esters 35

2.5.1.1 Fatty Alcohol Sulfates 36

2.5.1.2 Sulfated Fatty Acid Condensation Products 36

2.5.1.3 Sulfated Ethers 37

2.5.1.4 Sulfated Fats and Oils 38

2.5.2 Sulfonic Acid Salts 39

2.5.2.1 Aliphatic Sulfonates 39

2.5.2.2 Alkyl Aryl Sulfonates 40

2.5.2.3 α-Sulfocarboxylic Acids and Their Derivatives 42

2.5.2.4 Miscellaneous Sulfo-Ester and Amide Surfactants 43

2.5.2.5 Alkyl Glyceryl Ether Sulfonates 46

2.5.2.6 Lignin Sulfonates 46

2.5.3 Carboxylate Soaps and Detergents 46

2.5.4 Phosphoric Acid Esters and Related Surfactants 48

2.6 Cationic Surfactants 49

2.7 Nonionic Surfactants 51

2.7.1 Polyoxyethylene-Based Surfactants 51

2.7.2 Derivatives of Polyglycerols and Other Polyols 52

2.7.3 Block Copolymer Nonionic Surfactants 54

2.7.4 Miscellaneous Nonionic Surfactants 54

2.8 Amphoteric Surfactants 55

2.8.1 Imidazoline Derivatives 56

2.8.2 Surface-Active Betaines and Sulfobetaines 57

2.8.3 Phosphatides and Related Amphoteric Surfactants 58

3 Surfactant Chemical Structures: Putting the Pieces Together 61

3.1 Surfactant Building Blocks 61

3.2 A Surfactant Family Tree 63

3.2.1 The Many Faces of Dodecane 63

3.3 Common Surfactant Hydrophobic Groups 66

3.3.1 The Natural Fatty Acids 67

3.3.2 Paraffins or Saturated Hydrocarbons 67

3.3.3 Olefins 67

3.3.4 Alkylbenzenes 68

3.3.5 Alcohols 69

3.3.6 Alkylphenols 70

3.3.7 Polyoxypropylene 70

3.3.8 Fluorocarbons 70

3.3.9 Silicone-Based Surfactants 72

3.3.10 Nonchemically Produced, a.k.a. “Natural” Surfactants 74

4 Natural Surfactants and Biosurfactants 75

4.1 What Makes a Surfactant “Natural”? 76

4.2 Surfactants Based on a Natural Sugar-Based Polar Head Groups 78

4.3 Biosurfactants 80

4.3.1 Biosurfactants as Nature Makes Them 80

4.3.2 Properties of Biosurfactants 81

4.3.3 Biosurfactant Classification 83

4.3.4 Some Aspects of Biosurfactant Production 84

4.3.5 Some Factors Affecting Biosurfactant Production 85

4.4 Biosurfactant Applications 87

4.5 Potential Limitations on the Commercial Use of Biosurfactants 90

4.6 Some Opportunities for Future Research and Development 90

4.7 Some Observations About the Future of Biosurfactants 90

5 Fluid Surfaces and Interfaces 93

5.1 Molecules at Interfaces 95

5.2 Interfaces and Adsorption Phenomena 97

5.2.1 A Thermodynamic Picture of Adsorption 97

5.2.2 Surface and Interfacial Tensions 99

5.2.3 The Effect of Surface Curvature 101

5.2.4 The Surface Tension of Solutions 102

5.2.5 Surfactants and the Reduction of Surface Tension 103

5.2.6 Efficiency, Effectiveness, and Surfactant Structure 105

6 Surfactants in Solution: Self-Assembly and Micelle Formation 115

6.1 Surfactant Solubility 116

6.2 The Phase Spectrum of Surfactants in Solution 119

6.3 The History and Development of Micellar Theory 123

6.3.1 Manifestations of Micelle Formations 124

6.3.2 Thermodynamics of Dilute Surfactant Solutions 127

6.3.3 Classical Theories of Micelle Formation 128

6.3.4 Free Energy of Micellization 129

6.4 Molecular Geometry and the Formation of Association Colloids 130

6.5 Experimental Observations of Micellar Systems 133

6.5.1 Micellar Aggregation Numbers 133

6.5.2 The Critical Micelle Concentration 135

6.5.3 The Hydrophobic Group 135

6.5.4 The Hydrophilic Group 143

6.5.5 Counterion Effects on Micellization 145

6.5.6 The Effects of Additives on the Micellization Process 146

6.5.6.1 Electrolyte Effects on Micelle Formation 147

6.5.6.2 The Effect of pH 148

6.5.6.3 The Effects of Added Organic Materials 149

6.5.7 The Effect of Temperature on Micellization 151

6.6 Micelle Formation in Mixed Surfactant Systems 153

6.7 Micelle Formation in Nonaqueous Media 154

6.7.1 Aggregation in Polar Organic Solvents 155

6.7.2 Micelles in Nonpolar Solvents 155

7 Beyond Micelles: Higher Level Self-Assembled Aggregate Structures 161

7.1 The Importance of Surfactant Phase Information 161

7.2 Amphiphilic Fluids 163

7.2.1 Liquid Crystalline, Bicontinuous, and Microemulsion Structures 163

7.2.2 “Classical” Liquid Crystals 165

7.2.3 Liquid Crystalline Phases in Simple Binary Systems 166

7.3 Temperature and Additive Effects on Phase Behavior 170

7.4 Some Current Theoretical Analyses of Novel Mesophases 171

7.5 Vesicles and Bilayer Membranes 171

7.5.1 Vesicles 173

7.5.2 Polymerized Vesicles 174

7.6 Biological Membranes 176

7.6.1 Some Biological Implications of Mesophases 176

7.6.2 Membrane Surfactants and Lipids 177

7.7 Microemulsions 179

7.7.1 Surfactants, Co-surfactants, and Microemulsion Formation 183

7.7.1.1 Ionic Surfactant Systems 183

7.7.1.2 Nonionic Surfactant Systems 184

7.7.2 Applications 185

8 Surfactant Self-Assembled Aggregates at Work 187

8.1 Solubilization in Surfactants Micelles 188

8.1.1 The “Geography” of Solubilization in Micelles 189

8.1.2 Surfactant Structure and the Solubilization Process 191

8.1.3 Solubilization and the Nature of the Additive 194

8.1.4 The Effect of Temperature on Solubilization Phenomena 196

8.1.5 The Effects of Nonelectrolyte Solutes 197

8.1.6 The Effects of Added Electrolyte 198

8.1.7 Miscellaneous Factors Affecting Micellar Solubilization 199

8.1.8 Hydrotropes 199

8.2 Micellar Catalysis 201

8.2.1 Micellar Catalysis in Aqueous Solution 201

8.2.2 Micellar Catalysis in Nonaqueous Solvents 203

9 Polymeric Surfactants and Surfactant–Polymer Interactions 205

9.1 Polymeric Surfactants and Amphiphiles 205

9.2 Some Basic Chemistry of Polymeric Surfactant Synthesis 207

9.2.1 The Modification of Natural Cellulosic Materials, Gums, and Proteins 207

9.2.2 Synthetic Polymeric Surfactants 208

9.3 Polymeric Surfactants at Interfaces: Structure and Methodology 213

9.4 The Interactions of “Normal” Surfactants with Polymers 214

9.4.1 Surfactant–Polymer Complex Formation 215

9.4.2 Nonionic Polymers 218

9.4.3 Ionic Polymers and Proteins 219

9.5 Polymers, Surfactants, and Solubilization 222

9.6 Surfactant–Polymer Interactions in Emulsion Polymerization 223

10 Emulsions 225

10.1 The Liquid–Liquid Interface 226

10.2 General Considerations of Emulsion Stability 227

10.2.1 The Lifetimes of Typical Emulsions 230

10.2.2 Theories of Emulsion Stability 232

10.3 Emulsion Type and the Nature of the Surfactant 233

10.4 Surface Activity and Emulsion Stability 235

10.5 Mixed Surfactant Systems and Interfacial Complexes 239

10.6 Amphiphile Mesophases and Emulsion Stability 242

10.7 Surfactant Structure and Emulsion Stability 245

10.7.1 The Hydrophile–Lipophile Balance (HLB) 245

10.7.2 Phase Inversion Temperature (PIT) 250

10.7.3 Application of HLB and PIT in Emulsion Formulation 251

10.7.4 The Effects of Additives on the “Effective” HLB of Surfactants 253

10.8 Multiple Emulsions 254

10.8.1 Nomenclature for Multiple Emulsions 254

10.8.2 Preparation and Stability of Multiple Emulsions 254

10.8.3 Pathways for Primary Emulsion Breakdown 255

10.8.4 The Surfactants and Phase Components 256

11 Foams and Liquid Aerosols 259

11.1 The Physical Basis for Foam Formation 260

11.2 The Role of Surfactant in Foams 263

11.2.1 Foam Formation and Surfactant Structure 266

11.2.2 Amphiphilic Mesophases and Foam Stability 268

11.2.3 The Effects of Additives on Surfactant Foaming Properties 269

11.3 Foam Inhibition 271

11.4 Chemical Structures of Antifoaming Agents 272

11.5 A Summary of the Foaming and Antifoaming Activity of Additives 273

11.6 The Spreading Coefficient 274

11.7 Liquid Aerosols 276

11.7.1 The Formation of Liquid Aerosols 276

11.7.1.1 Spraying and Related Mechanisms of Mist and Fog Formation 276

11.7.1.2 Nozzle Atomization 277

11.7.1.3 Rotary Atomization 278

11.7.2 Aerosol Formation by Condensation 279

11.7.3 Colloidal Properties of Aerosols 282

11.7.3.1 The Dynamics of Aerosol Movement 282

11.7.3.2 Colloidal Interactions in Aerosols 284

12 Solid Surfaces: Adsorption, Wetting, and Dispersions 287

12.1 The Nature of Solid Surfaces 287

12.2 Liquid Versus Solid Surfaces 290

12.3 Adsorption at the Solid–Liquid Interface 291

12.3.1 Adsorption Isotherms 292

12.3.2 Mechanisms of Surfactant Adsorption 293

12.3.2.1 Dispersion Forces 294

12.3.2.2 Polarization and Dipolar Interactions 295

12.3.2.3 Electrostatic Interactions 296

12.3.3 The Electrical Double Layer 297

12.4 The Mechanics of Surfactant Adsorption 298

12.4.1 Adsorption and the Nature of the Adsorbent Surface 299

12.4.2 Nonpolar, Hydrophobic Surfaces 299

12.4.3 Polar, Uncharged Surfaces 300

12.4.4 Surfaces Having Discrete Electrical Charges 301

12.5 Surfactant Structure and Adsorption from Solution 303

12.5.1 Surfaces Possessing Strong Charge Sites 303

12.5.2 Adsorption by Uncharged, Polar Surfaces 306

12.5.3 Surfactants at Nonpolar, Hydrophobic Surfaces 306

12.6 Surfactant Adsorption and the Character of Solid Surfaces 307

12.7 Wetting and Related Phenomena 308

12.7.1 Surfactant Manipulation of the Wetting Process 311

12.7.2 Some Practical Examples of Wetting Control By Surfactants 314

12.7.3 Detergency and Soil Removal 314

12.7.4 The Cleaning Process 314

12.7.5 Soil Types 315

12.7.6 Solid Soil Removal 316

12.7.7 Liquid Soil Removal 317

12.7.8 Soil Re-deposition 318

12.7.9 Correlations of Surfactant Structure and Detergency 319

12.7.10 Nonaqueous Cleaning Solutions 320

12.8 Suspensions and Dispersions 321

13 Special Topics in Surfactant Applications 323

13.1 Surfactants in Foods 323

13.1.1 The Legal Status of Surfactants in Food Products 324

13.1.2 Typical Food Emulsifier Sources 324

13.1.3 Chemical Structures of Some Important Food Emulsifiers 326

13.1.3.1 Monoglycerides 326

13.1.3.2 Derivatives of Monoglycerides 327

13.1.3.3 Derivatives of Sorbitol 329

13.1.3.4 Polyhydric Emulsifiers 330

13.1.3.5 Polyglycerol Esters 331

13.1.3.6 Sucrose Esters 331

13.1.3.7 Anionic Food Emulsifiers 332

13.1.3.8 Lecithin 333

13.2 Some Important Functions of Surfactants in Food Products 334

13.2.1 Emulsifiers as Crystal Modifiers in Food 335

13.2.2 Bakery Products 337

13.2.2.1 Anti-staling Agents 338

13.2.2.2 Starch–Emulsifier Complexation 339

13.2.2.3 Dough Strengtheners 340

13.2.2.4 Aerating Agents 341

13.2.3 Emulsifier Use in Dairy and Nondairy Substitutes 342

13.2.3.1 What Makes Milk “Milk”? 343

13.2.3.2 Surfactant Uses in Cheeses and Cheese Substitutes 344

13.2.3.3 Surfactant Use in Deserts and Yogurts 344

13.2.3.4 Butter and Margarine 344

13.2.3.5 Whipped Cream and Nondairy Whipped Toppings 345

13.2.3.6 Dairy Drinks 347

13.2.3.7 Ice Cream 347

13.2.3.8 Coffee Whiteners 348

13.2.4 Protein Emulsifiers in Foods 349

13.2.4.1 Proteins as Foam Stabilizers 351

13.2.4.2 Proteins as Emulsifying Agents 352

13.2.4.3 Protein–Low Molecular Weight Emulsifier Interactions 353

13.3 Pharmaceutical and Medicinal Applications 354

13.4 Petroleum and Natural Gas Extraction 355

13.4.1 Enhanced Oil Recovery 356

13.4.2 Hydraulic Fracturing or “Fracking” 358

13.5 Paints and Surface Coatings 359

13.5.1 Interfaces in Paints and Coatings 360

13.5.2 Wetting and Dispersing Additives 361

13.5.3 Wetting Agents 363

13.5.4 Dispersing Agents 363

13.5.5 Surface Wetting with Silicone Surfactants 366

14 “Multiheaded” Amphiphiles: Gemini and Bolaform Surfactants 369

14.1 Two (or More) Can Be Better Than One 369

14.1.1 Structural Characteristics of Gemini Surfactants 370

14.1.2 Some Synthetic Pathways to Gemini Structures 371

14.1.3 Important Surfactant Properties of Gemini Surfactants 372

14.1.4 Some “Outside the Box” Potential Applications of Gemini Surfactants 375

14.2 Bolaform Surfactants 377

14.3 Chemical Structures and Self-Assembly Patterns 380

Chapter Bibliographies 381

Index 389