The textbook seeks to bring readers with no prior knowledge or experience in interfacial phenomena, colloid science or nanoscience to the point where they can comfortably enter the current scientific and technical literature in the area.

Designed as a pedagogical tool, this book recognizes the cross-disciplinary nature of the subject. To facilitate learning, the topics are developed from the beginning with ample cross-referencing. The understanding of concepts is enhanced by clear descriptions of experiments and provisions of figures and illustrations.


Contents:
Fluid Interfaces and Capillarity
Thermodynamics of Interfacial Systems
Solid-Liquid Interactions
Colloidal Systems: Phenomenology and Characterization
Electrical Properties of Interfaces
Interaction Between Colloid Particles
Rheology of Dispersions
Emulsions and Foams
Interfacial Hydrodynamics


Readership: Senior undergraduate and graduate students in chemistry, physics, materials science, chemical engineering, civil engineering, mechanical engineering and related fields.

AN INTRODUCTION TO INTERFACES AND COLLOIDS - The Bridge to Nanoscience
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CONTENTS
Preface vi i
I. INTRODUCTION 1
A. Interfaces 1
B. Colloids 4
C. The bridge to nanoscience 10
1. What is gnanoscience?h 10
2. Nanostructures and assemblies 12
3. Generic nanoscience 17
4. New tools of generic nanoscience 18
5. The plan 22
II. FLUID INTERFACES AND CAPILLARITY 23
A. Fluid interfaces: Youngfs membrane model 23
1. The thinness of interfaces 23
2. Definition of surface tension 25
B. The surface tension of liquids 26
1. Pure liquids 26
2. Temperature dependence of surface tension 27
3. Surface tension of solutions 29
C. Intermolecular forces and the origin of surface tension 31
1. Van der Waals forces 31
2. Surface tension as gunbalancedh intermolecular forces;
the Hamaker constant 35
3. Pressure deficit in the interfacial layer; Bakkerfs equation 37 4. Components of the surface tension 41
D. Interfacial tension 43
1. Experimental interfacial tension 43
2. Combining rules for interfacial tension 43
E. Dynamic surface tension 46
F. Capillary hydrostatics: the Young-Laplace Equation 46
1. Capillary pressure: pressure jump across a curved fluid
interface 46
2. The curvature of a surface 48
3. Derivation of the Young-Laplace equation 53
4. Boundary conditions for the Young-Laplace equation 55
G. Some solutions to the Young-Laplace equation 57
1. Cylindrical surfaces; meniscus against a flat plate 57
2. Axisymmetric and other surfaces 59
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x CONTENTS
3. Nondimensionalization of the Young-Laplace equation;
the Bond number 59
4. Saddle-shaped surfaces 62
H. The measurement of surface and interfacial tension 64
1. Geometric vs. force methods 64
2. Capillary rise 65
3. Sessile drop and pendant drop 68
4. Du Nouy ring detachment 68
5. Wilhelmy slide 69
6. Langmuir film balance 70
7. Drop weight (or volume) 71
8. Maximum bubble pressure and dynamic surface tension 72
9. The pulsating bubble gsurfactometerh 74
10. Elliptical (vibrating) jet 74
11. Contracting circular jet 75
12. Problems with interfacial tension measurement 75
13. Spinning drop method 76
I. Forces on solids in contact with liquids: capillary interactions 76
1. Liquid bridges 76
2. Shared menisci 80
J. Effect of curvature on the equilibrium properties of bulk
liquids: the Kelvin Effect 84
1. The vapor pressure of small droplets and liquids in pores 84
2. The effect of curvature on boiling point 86
3. Capillary condensation 86
4. Nucleation 88
K. Thin liquid films 91
1. Disjoining pressure and its measurement 91
2. The molecular origin of disjoining pressure 94
3. The disjoining pressure isotherm 98
4. The augmented Young-Laplace equation 101
SOME FUN THINGS TO DO: CHAPTER 2 103
III. THERMODYNAMICS OF INTERFACIAL SYSTEMS 107
A. The thermodynamics of simple bulk systems 107
1. Thermodynamic concepts 107
2. The simple compressible system 108
B. The simple capillary system 110
1. The work of extension 110
2. Heat effects; abstract properties; definition of
boundary tension 111
C. Extension to fluid-solid interfacial systems 114
1. The work of area extension in fluid-solid systems 114
2. Compound interfacial systems; Youngfs equation 116
D. Multicomponent interfacial systems 119
1. The Gibbs dividing surface and adsorption 119
AN INTRODUCTION TO INTERFACES AND COLLOIDS - The Bridge to Nanoscience
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CONTENTS xi
2. Immiscible interfacial systems 123
3. The measurement of adsorption 124
4. The phase rule; descriptive equations for binary
interfacial systems 127
E. The Gibbs adsorption equation 128
F. Surface tension of solutions 134
1. Ideal-dilute capillary systems 134
2. Moderately dilute capillary systems 135
G. Surface active agents (surfactants) and their solutions 137
1. The structure of different types of surface active agents 137
2. Solutions of non-electrolyte surfactants 144
3. Solutions of electrolyte surfactants 147
H. Self-assembly of surfactant monomers in solution 148
1. Formation of micelles: critical micelle concentration (CMC) 148
2. Solubilization 160
I. Micelle morphology, other self-assembled structures, and
concentrated surfactant solutions 164
1. Micellar shape and the Critical Packing Parameter (CPP) 164
2. Beyond micelles: other self-assembled structures 166
3. Concentrated surfactant solutions; liquid crystalline
mesophases 170
4. Kinetics of micellization and other self-assembly processes 171
J. Dynamic surface tension of surfactant solutions 171
1. Diffusion-controlled adsorption 171
2. Finite adsorption-desorption kinetics 175
K. Insoluble (Langmuir) monolayers 176
1. Formation of monolayers by spontaneous spreading 176
2. Hydrodynamic consequences of monolayers:
Gibbs elasticity 177
3. ƒÎ-A isotherms of insoluble monolayers 178
4. Langmuir-Blodgett films 182
5. Transport properties of monolayers 184
L. The thermodynamics of fluid-solid interfacial systems revisited 186
1. The concept of interfacial energy and its measurement in
fluid-solid systems 186
2. Adsorption of non-polymeric molecules at the solid-liquid
interface 191
3. Experimental measurement of small molecule solid-liquid
adsorption 201
4. Adsorption of polymers at the solid-liquid interface 202
SOME FUN THINGS TO DO: CHAPTER 3 207
IV. SOLID-LIQUID INTERACTIONS 214
A. Wettability and the contact angle: Young’s Equation 214
1. Importance of wetting; definition of contact angle 214
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2. Youngfs equation revisited; classification of wetting and
contact angle values 216
B. Contact angle hysteresis 218
1. Origins of hysteresis: roughness and heterogeneity 218
2. Complexity of real surfaces: texture and scale 221
3. Wenzel equation for rough surfaces 223
4. Cassie-Baxter analysis of heterogeneous surfaces;
composite surfaces and ultra-hydrophobicity 224
5. The dynamic contact angle; Tannerfs law 227
C. Methods for measuring the contact angle 229
1. Optical or profile methods: contact angle goniometry 229
2. Force methods: contact angle tensiometry 231
3. Dynamic contact angle measurement 235
D. Relation of wetting behavior to surface chemical constitution 236
1. Zisman plots; the critical surface tension 236
2. The wettability series 238
3. Estimates of surface energies from contact angle data
or vice versa 239
4. Thermodynamics of solid-liquid contact: work of adhesion,
work of wetting and work of spreading; the Young-Dupre
equation 243
5. The promotion or retardation of wetting: practical
strategies 245
E. Spreading of liquids on solid surfaces 250
1. Criteria for spontaneous spreading; spreading morphology 250
2. Temperature effects of wetting; heats of immersion and
wetting transitions 254
3. The kinetics of spreading on smooth surfaces 255
4. Spreading agents; superspreaders 257
F. The relationship of wetting and spreading behavior to adhesion 258
1. Definition of adhesion; adhesion mechanisms 258
2. The gLaws of Molecular Adhesionh 259
3. gPractical adhesionh vs. gthermodynamic adhesionh 261
4. The importance of wetting (contact angle) to practical
adhesion 263
5. The optimization of thermodynamic contact adhesion 264
6. Acid-base effects in adhesion 267
7. Contact mechanics; the JKR method 272
G. Heterogeneous nucleation 277
H. Processes based on wettability changes or differences 279
1. Detergency 279
2. Flotation 280
3. Selective or gsphericalh agglomeration 281
4. Offset lithographic printing 282
I. Wicking flows (capillary action) and absorbency 284
1. Wicking into a single capillary tube 284
AN INTRODUCTION TO INTERFACES AND COLLOIDS - The Bridge to Nanoscience
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CONTENTS xiii
2. Wicking in porous media 286
3. Practical strategies for promoting absorbency 290
4. Immiscible displacement 292
5. Mercury porosimitry 292
6. Motion of liquid threads 293
7. Surface wicking; spreading over rough or porous surfaces 295
J. Particles at interfaces 297
1. Particles at solid-fluid interfaces: effects on wetting and
spreading 297
2. The disposition of particles at fluid interfaces 297
3. Particle-assisted wetting 299
4. Pickering emulsions 303
5. Armored bubbles and liquid marbles 305
6. Janus particles and nanoparticles at fluid interfaces 306
K. The description of solid surfaces 309
1. Solid surface roughness 309
2. Fractal surfaces 310
3. Surface texture 313
4. Measurement of surface roughness and texture by stylus
profilometry 314
L. Optical techniques for surface characterization 315
1. Optical microscopy 315
2. Optical profilometry 318
3. Confocal microscopy 318
4. Electron microscopy 319
5. Near-field scanning optical microscopy (NSOM) 320
M. Scanning probe microscopy (SPM) 321
1. Scanning Tunneling Microscopy (STM) 322
2. Atomic Force Microscopy (AFM) 324
N. Surface area of powders, pore size distribution 331
O. Energetic characterization of solid surfaces: Inverse Gas
Chromatography (IGC) 333
SOME FUN THINGS TO DO: CHAPTER 4 338
V. COLLOIDAL SYSTEMS: PHENOMENOLOGY AND
CHARACTERIZATION 345
A. Preliminaries 345
1. Definition and classification of colloids 345
2. General properties of colloidal dispersions 346
3. Dense vs. dilute dispersions 349
B. Mechanisms of lyophobic colloid instability 351
1. Phase segregation: the "phoretic processes" 351
2. Thermodynamic criteria for stability 353
3. Aggregation 353
4. Coalescence 355
5. Particle size disproportionation 356
AN INTRODUCTION TO INTERFACES AND COLLOIDS - The Bridge to Nanoscience
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xiv CONTENTS
C. Preparation of colloid particles and colloidal dispersions 358
1.Classification of preparation strategies for lyophobic
colloids 358
2. Top-down strategies 360
3. Bottom-up strategies 365
D. Morphology of colloids: particle size, size distribution, and
particle shape 371
1. Description of particle size distributions 371
2. Distributions based on different size variables and
weighting factors 375
3. Normal (Gaussian) and log-normal distributions 379
4. Particle shape 382
E. Sedimentation and centrifugation 387
1. Individual particle settling: Stokesf law 387
2. Multi-particle, wall and charge effects on sedimentation 389
3. Differential sedimentation; particle size analysis 391
4. Centrifugation 395
F. Brownian motion; sedimentation-diffusion equilibrium 397
1. Kinetic theory and diffusion 397
2. Brownian motion 399
3. Sedimentation (centrifugation) . diffusion equilibrium 403
4. Practical retrospective regarding sedimentation and
other phoretic processes 407
G. Measurement of particle size and size distribution: overview 409
1. Classification of methods 409
2. Microscopy 410
H. Light scattering 413
1. Classical (static) light scattering 413
2. Rayleigh scattering 414
3. Turbidity 418
4. Rayleigh-Gans-Debye (RGD) scattering 421
5. Mie scattering 427
6. Fraunhofer diffraction; laser diffraction 429
7. Inelastic scattering: absorbance; the Raman effect 431
8. Scattering from denser dispersions 436
9. Dynamic Light Scattering (Photon Correlation
Spectroscopy) 437
10. Dynamic light scattering from denser dispersions 442
I. Aperture, chromatographic and acoustic methods for
particle sizing 444
1. Aperture (one-at-a-time) methods 444
2. Chromatographic methods 446
3. Acoustic methods 448
SOME FUN THINGS TO DO: CHAPTER 5 450
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CONTENTS xv
VI. ELECTRICAL PROPERTIES OF INTERFACES 455
A. Origin of charge separation at interfaces 455
1. Overview 455
2. Preferential adsorption/desorption of lattice ions 456
3. Specific adsorption of charged species 459
4. Ionization of surface functional groups 460
5. Isomorphic substitution 461
6. Accumulation/depletion of electrons 462
7. Interface charging in non-aqueous systems 463
B. Electric double layer formation and structure 466
1. The Helmholtz model; electrostatic units 466
2. The Gouy-Chapman model; Poisson-Boltzmann equation 467
3. Boundary conditions to the Poisson-Boltzmann equation 475
4. Double layers at spherical and cylindrical surfaces 477
5. The free energy of double layer formation 478
6. The Stern model; structure of the inner part of the
double layer 480
7. The mercury solution interface; electrocapillarity and
refinements to the double layer model 483
8. Oriented dipoles at the interface: the ƒÔ-potential 485
C. Electrostatic characterization of colloids by titration methods 487
1. Colloid titrations 487
2. Potentiometric titrations 488
3. Conductometric titrations 492
4. Donnan equilibrium and the suspension effect 493
D. Electrokinetics 496
1. The electrokinetic phenomena 496
2. The zeta potential and its interpretation 500
3. Electrokinetic measurements; micro-electrophoresis 503
4. Relationship of zeta potential to electrophoretic mobility 508
5. Electrokinetic titrations 512
6. Electro-acoustic measurements 514
E. Dielectrophoresis and optical trapping 516
1. Dielectrophoresis 516
2. Electrorotation and traveling wave dielectrophoresis 519
3. Optical trapping; laser tweezers 520
SOME FUN THINGS TO DO: CHAPTER 6 523
VII. INTERACTION BETWEEN COLLOID PARTICLES 525
A. Overview and rationale 525
B. Long-range van der Waals interactions 526
1. The Hamaker (microscopic) approach 526
2. Retardation 530
3. The Lifshitz (macroscopic) approach 532
4. Measurement of Hamaker constants 535
C. Electrostatic interactions; DLVO theory 540
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xvi CONTENTS
1. Electrostatic repulsion between charged flat plates 540
2. Electrostatic interactions between curved surfaces;
the Derjaguin approximation 544
3. DLVO theory: electrocratic dispersions 547
4. Jar testing, the Schulze-Hardy rule and agreement
with theory 552
5. The Hofmeister series; ion speciation and ionic
specific adsorption 554
6. Repeptization 556
7. Interaction between dissimilar surfaces: hetero-aggregation 558
D. Kinetics of aggregation 560
1. Classification of aggregation rate processes and
nomenclature 560
2. Smoluchowski theory of diffusion-limited aggregation 561
3. The hydrodynamic drainage effect 566
4. Orthokinetic (shear flow induced) aggregation 568
5. Reaction-limited (slow) aggregation; the stability ratio W 569
6. Secondary minimum effects 571
7. Kinetics of hetero-aggregation 573
8. Measurement of early-stage aggregation kinetics (W) 574
9. Surface aggregation 577
10. Electrostatic stabilization and aggregation rates in
apolar media 579
E. Steric stabilization and other colloid-polymer interactions 582
1. Polymer adsorption and steric stabilization 582
2. Thermodynamic considerations: enthalpic vs. entropic
effects 585
3. Fischer theory 587
4. Steric repulsion plotted on DLVO coordinates 591
5. Electro-steric stabilization 595
6. Bridging flocculation 596
7. Depletion flocculation 597
8. Electrophoretic displays; electronic paper 599
F. The kinetics (and thermodynamics) of flocculation 601
G. Other non-DLVO interaction forces 603
H. Aggregate structure evolution; fractal aggregates 607
1. Stages of the aggregation process 607
2. Fractal aggregates 608
3. The effect of particle size on aggregation phenomena;
coating by nanoparticles 612
SOME FUN THINGS TO DO: CHAPTER 7 613
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CONTENTS xvii
VIII. RHEOLOGY OF DISPERSIONS 616
A. Rheology: scope and definitions 616
B. Viscometry 617
1. Newtonfs law of viscosity 617
2. Measurement of viscosity 618
C. The viscosity of colloidal dispersions 622
1. Dilute dispersions; Einstein theory 622
2. Denser dispersions of non-interacting particles 623
3. Dilute dispersions of non-spherical particles 625
D. Non-Newtonian rheology 626
1. General viscous behavior of dispersions of non-interacting
particulates 626
2. Fluids with a yield stress 630
3. Time-dependent rheology 632
4. Viscoelasticity 633
E. Electroviscous effects 637
SOME FUN THINGS TO DO: CHAPTER 8 640
IX. EMULSIONS AND FOAMS 643
A. General consideration of emulsions 643
1. Classification of emulsions 643
2. Emulsifiers and emulsion stability 644
3. Thermodynamics of emulsification/breakdown 649
4. Preparation of emulsions 651
B. O/W or W/O emulsions? 652
1. Rules of thumb 652
2. The hydrophile-lipophile balance (HLB) and related scales 654
3. Double (or multiple) emulsions 659
C. Application of emulsions 661
1. Formation/breaking in situ 661
2. Demulsification 663
D. Microemulsions 664
1. Distinction between microemulsions and macro emulsions 664
2. Phase behavior of microemulsion systems 666
3. Ultra-low interfacial tension 671
4. Interfacial film properties in microemulsion systems 672
E. General consideration of foams 673
1. Nature and preparation of foams 673
2. Stages in foam lifetime 675
3. Stability mechanisms 676
4. Foam behavior and foaming agents 681
5. Antifoam action 684
6. Froth flotation 686
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xviii CONTENTS
7. Foaming in non-aqueous media; general surface activity
near a phase split 687
SOME FUN THINGS TO DO: CHAPTER 9 691
X. INTERFACIAL HYDRODYNAMICS 695
A. Unbalanced forces at fluid interfaces 695
1. Unbalanced normal forces 695
2. Tangential force imbalances: the Marangoni effect 696
3. Boundary conditions at a fluid interface 702
B. Examples of Interfacial Hydrodynamic Flows 705
1. The breakup of capillary jets 705
2. Steady thermocapillary flow 712
3. The motion of bubbles or drops in a temperature gradient 714
4. Marangoni instability in a shallow liquid pool.Benard cells 718
C. Some Practical Implications of the Marangoni Effect 728
1. Marangoni effects on mass transfer 728
2. Marangoni drying 732
3. Marangoni patterning 733
D. The Effect of Surface Active Agents 735
1. Gibbs elasticity 735
2. The boundary conditions describing the effects
of surfactants 737
3. The effect of surfactants on bubble or droplet circulation 740
4. The effect of surfactants on the stability of a pool heated
from below 745
SOME FUN THINGS TO DO: CHAPTER 10 748
Appendix 1: EXERCISES 753
Appendix 2: THE TOP TEN 767
Appendix 3: OTHER SOURCES 771
Index 773