THE AQUEOUS PHASE BEHAVIO ROF SURFACTANTS

ROBERT G . LAUGHLIN

Foreword

xvii

Preface

xix

Acknowledgements

xxi

Part I BACKGROUN D

Chapter 1 Introduction

31 .1 The subject material of phase science

3

1 .2 The distinctive characteristics of surfactant phase science

4

1 .3 The .nature of the complexity of surfactant phase behavior

51 .4 The influence of system variables and of molecular structure

61 .5 Sources of data

61 .6 The book's organization

71 .7 The treatment of fundamentals

81 .8 The information content of phase diagrams

91 .9 The philosophy

1 0References

1 1

Chapter 2 The role of phase science within physical science

1 32.1 A general view of physical science

1 32 .2 The chemical and physical aspects of physical chemistry

1 42 .2 .1 The chemical aspect

1 52 .2 .2 The physical aspect

1 72 .3 The dimensions of the physical and colloid science of surfactants

1 82 .4 The structural aspects of physical science

1 82 .4 .1 Molecular structure

1 92 .4 .2 Conformational structure

1 92 .4 .3 Phase structure

2 12 .4 .3 .1 Defining conformational and phase structure

2 1

2 .4 .4 Colloidal structure

2 12 .4 .4 .1 The classes of colloidal structures

22

2 .4 .4 .2 The subclasses of irreversible colloidal structures

2 3

2.5 The thermodynamic aspect of physical science

2 32.6 The kinetic and mechanistic aspects of physical science

242.7 The colloidal aspect of physical science

26

2 .7 .1 The stability of colloidal structure

26

2.8 The theoretical aspect of physical science

27

2.9 Interrelationships among the different aspects

2 7

2 .10 The collective value

28

2.11 Summary

2 9

References

3 0

Part II PHYSICAL CHEMISTRY

Chapter 3 The thermodynamics of immiscibility

353 .1 The state variables and functions

3 5

3 .2 Heat, work, and heat capacities

3 73 .3 Partial molar quantities : the chemical potential

40

3 .4 The "extensive " and "intensive" classes of thermodynamicvariables

4 1

3 .5 The "density" and "field" classes of thermodynamic variables

42

3 .6 Defining systems and mixtures

44

3 .7 The thermodynamics of unary systems

4 5

3 .8 Composition units

4 7

3 .9 The ideal mixing approach

4 9

3 .10 The ideal free energy of mixing

5 1

3 .11 The ideal "reduced free energy of mixing" function

5 2

3 .12 The form of the ideal free energy of mixing function

5 2

3 .13 Nonideal mixing with miscibility in all proportions

5 3

3 .14 Partial miscibility

5 4

3 .15 The condition of equilibrium for coexisting phases

5 4

3 .16 Multiple miscibility gaps

5 6

3 .17 A pure component as a coexisting phase

5 8

3 .18 Three coexisting phases at eutectics

59

3 .19 Three coexisting phases at peritectics

6 1

3 .20 Total immiscibility : the container issue

6 2

3 .21 The thermodynamics of three-phase discontinuities

6 3

References

6 5

Chapter 4 Phase diagrams and the Phase Rule

6 74.1 The dimensions of phase behavior

6 7

4 .2 Phase diagrams of binary systems

6 8

4 .3 Reading and interpreting binary diagrams

69

4 .4 Phase diagrams of unary systems

70

4 .5 The Phase Rule

70

4 .6 The number of components, C

7 1

4 .7 The number of phases, P

7 34 .8 The degrees of freedom or variance, F

7 3

4 .8 .1 Variance in a one-phase region in a binary system

74

4 .8 .2 Variance in a two-phase region in a binary system

7 4

4 .8 .3 Variance at three-phase discontinuities between condense d

phases

7 5

4 .8 .4 Variance in mixtures containing an equilibrium gas phase

7 6

4 .8 .5 Variance in four-phase mixtures in a binary system

7 74 .8 .6 The existence of variance within phases of fixed

composition

7 7

4 .9 Phase fractions in two-phase regions : the lever rule

78

4.10 Phase reactions at isothermal discontinuities

7 94 .11 Phase fractions at isothermal discontinuities : the Tammann triangle 804.12 The alternation rule

8 24 .13 Isothermal discontinuities as "thermodynamic stop-signs"

8 34.14 The kinds of isothermal discontinuities

8 34 .15 Some different ways of using the Phase Rule

8 54 .16 A comparison of isothermal and isoplethal process paths

8 74 .17 Boundary conditions for use of the Phase Rule

8 74 .17 .1 The condition of equilibrium of state

8 74 .17 .1 .1 Equilibrium of state and colloidal structure

8 84 .17 .2 The dynamic aspect of equilibrium

8 94 .17 .3 Fluctuations in space and time within equilibrium phases

8 94 .17 .4 The influence of surface energies

9 04 .17 .5 The influence of external fields

9 14 .18 The concepts of "phase" and "interface"

9 24 .18 .1 Spatial composition profiles

9 24 .19 Suggested definitions of "phase" and "interface"

9 74.20 Tensions within phases and at interfaces

9 9References

9 9

Chapter 5 The characteristic features of surfactant phase behavior

1025 .1 Thermal energies, water free energies, and chemical potentials

10 25 .2 The thermal and chemical stability problem

10 35 .3 Solubility boundaries

10 55 .4 Crystal solubility: the Krafft boundary and the Krafft eutectic

1065 .4 .1 The Krafft boundary, Krafft points, and micellization

10 65 .4 .2 The slope of the Krafft plateau

11 15 .4 .3 The solubility at the Krafft eutectic

11 35 .4 .4 Metastable Krafft boundaries and Krafft eutectics

11 45 .4 .5 A definition of the Krafft boundary and Krafft eutectic

11 65 .4 .6 The significance of the Krafft eutectic

11 65 .5 The phase behavior of surfactant crystal phases

11 75 .5 .1 Dry crystals

11 75 .5 .2 The dry soap phases

11 75 .5 .3 Dry (thermotropic) liquid crystal phases

11 85 .5 .4 Polymorphic states : equilibrium and metastable

11 95 .6 Liquid crystal regions

1205 .6 .1 The upper temperature limit of liquid crystal regions

12 15 .6 .2 The lower temperature limit of liquid crystal regions

1235 .6 .3 The lower temperature limit of liquid crystal region s

when the Krafft boundary is metastable

1245 .6 .4 The lower azeotropic temperature limit of liquid crysta l

regions

1245 .6 .5 The factors that govern the temperature limits of liqui d

crystal regions

12 55 .6 .6 The composition limits of liquid crystal regions

1275 .6 .7 Phase reactions that occur during isothermal mixing

1285 .6 .8 The liquid crystal solubility boundary

130

5 .6 .9 The factors that govern the composition limits of liqui dcrystal regions

13 15 .6 .10 Multiple liquid crystal regions

1325 .6 .11 Phase reactions along concentrated isoplethal process paths

13 55 .7 The influence of crystal hydrates on phase behavior

1365 .8 The squeezing together of liquid crystal regions

13 85 .9 The influence of dry liquid crystal states

13 95 .10 "Cloud points" and the liquid/liquid miscibility gap

13 95 .10 .1 Lower consolute boundaries and lower critical points

1405 .10 .2 Upper consolute boundaries and upper critical points

14 15 .10 .3 The closed loop of coexistence

1425 .10 .4 A comparison of lower and upper consolute boundaries

1435 .10 .5 Interference between the liquid/liquid miscibility gap an d

the Krafft boundary

14 45 .10 .6 Interference between the liquid/liquid miscibility gap an d

liquid crystal regions

1455 .10 .7 The "pivotal phase behavior" concept

1485 .11 Summary

15 0References

15 1

Chapter 6 The kinetic and mechanistic aspects of surfactant phase behavior

1556 .1 General principles

15 56 .2 The role of heat and mass transport : the engineering factors

15 66 .3 Rates of phase transformations along isoplethal paths

15 76 .3 .1 The formation of a crystal from a fluid state

15 76 .3 .2 The formation of a liquid or liquid crystal from another state 15 86 .3 .3 T jump experiments from one state to another

15 96 .4 The rates of phase transformations along isothermal paths

15 96 .5 The mechanisms of surfactant phase reactions

16 16 .5 .1 Mechanism of the peritectic decomposition of crysta l

hydrates

16 16 .5 .2 Possible mechanisms at eutectic discontinuities

16 36 .6 Summary

163References

16 3

Chapter 7 Surfactant phase behavior and relative humidity

1657 .1 Water activities, activity coefficients, and the Phase Rule

16 57 .1 .1 The equivalence of water activities and relative humidities

1677 .2 Water activity profiles in the sodium chloride-water system

1687 .3 The use of water activity profiles to predict phase compositions

17 17 .4 The water activity profile at 25°C in the C12E6-water system

1727 .5 The order of phase transitions in the C 12 E6 -water system

174References

176

Part III STRUCTURAL CHEMISTRY

Chapter 8 The structures and properties of surfactant phases

18 18 .1 Introduction

181

8 .2 Optical and structural isotropy and anisotropy

1828 .3 The crystal phases

1848 .3 .1 The bilayer crystal structure

18 68 .3 .1 .1 The molecules within bilayers

1868 .3 .1 .2 Assembling the bilayer

19 08 .3 .1 .3 Assembling the bulk phase from bilayers

19 28 .3 .2 Nonbilayer crystal structures

19 38 .3 .3 Polymorphic crystal phases

19 68 .3 .4 Stoichiometric crystal hydrates

19 88 .3 .4 .1 Nonstoichiometric crystal hydrates

19 98 .3 .5 Plastic crystal phases

20 08 .4 The liquid crystal phases

20 08 .4.1 General properties

20 08 .4 .2 Rheological properties

20 18 .4 .3 Optical properties

20 28 .4 .4 The theoretical number of liquid crystal structures

20 38 .4 .5 Lyotropic and thermotropic liquid crystals

20 48 .4 .6 The lamellar liquid crystal phase

20 58 .4 .7 The Pp, Lp, and L a phases

21 08 .4 .8 The bicontinuous cubic phase

21 18 .4 .9 The "normal" hexagonal phase and the "rectangular"

phase

21 38 .4 .10 The discontinuous cubic phase

21 58 .4 .11 Phases more concentrated than the lamellar phase :

the "inverted" bicontinuous cubic phase

21 88 .4 .12 The "inverted" hexagonal phase

21 88 .4 .13 The lyotropic nematic phases

21 98 .4 .14 The "intermediate" phases

2208 .4 .15 The "K" phase

2208 .5 The liquid phases

2208 .5 .1 Binary aqueous surfactant liquids

2208 .5 .2 Ternary aqueous surfactant liquids (microemulsions)

2248 .6 The nomenclature systems for surfactant phase structures

22 58 .7 The absences of phase structures

2258 .8 The factors which define surfactant phase behavior

2288 .8 .1 Models for the relationship between phase structure and

molecular structure

2298 .8 .2 Theories of phase behavior

23 08 .8 .3 Relevant experimental observations

23 18 .9 The broad picture

23 2References

23 3

Part IV MOLECULAR CORRELATION S

Chapter 9 Surfactant and nonsurfactant behavior in amphiphilic molecules

24 19 .1 The concept of "amphiphilic" molecular structure

24 19 .2 The structural features which influence phase behavior

24 19 .3 The concept of hydrophilicity

242

9.4 The range of polarity within dipolar functional groups

2439 .4 .1 The electronic structure of dipolar bonds

24 49 .4 .2 The polarity of ionic and zwitterionic groups

24 69.5 A process for recognizing hydrophilicity

24 89 .5 .1 The phase criteria of surfactant behavior

25 09.6 The existence of hydrophilicity vs . molecular structure

25 29 .6 .1 Hydrophilicity in monofunctional amphiphilic molecules

25 29 .6 .2 Hydrophilicity in polyfunctional amphiphilic molecules

25 39.7 A structural classification of hydrophilic groups

25 7References

25 7

Chapter 10 Hydrophilicity and proximate substituent effects on phase behavior

25910 .1 Introduction

25 910 .2 The intensive variation of hydrophilicity

25 910 .2 .1 Extracting intrinsic hydrophilicity from phase information

25 910 .2 .2 The influence of substituents on phase behavior

26 110 .3 Choosing molecules for the evaluation of intrinsic hydrophilicity

26810 .4 Supporting evidence for relative hydrophilicity data

26 910 .5 The relative intrinsic hydrophilicities of hydrophilic groups

27 110 .5 .1 Ionic class, anionic subclass

27 110 .5 .2 Ionic class, cationic subclass

27 810 .5 .3 Nonionic class, zwitterionic subclass

28010 .5 .3 .1 Influence of the anionic substituent

28 310 .5 .3 .2 Influence of the tether

28 510.5 .4 Nonionic class, semipolar subclass

29010 .5 .4 .1 Group V and VI oxides

29 010 .5 .4 .2 Phosphinyl (P --+ 0) esters and amides

29210 .5 .4 .3 N-Terminal hydrophilic groups

29 510 .5 .4 .4 Ammonioamidates

29 810 .5 .5 Nonionic class, single bond subclass

30010 .5 .5 .1 Polyhydroxy surfactants

30 110 .5 .5 .2 Polyoxyethylene surfactants

30 310 .6 The concept of hydrophilicity

30 810 .6 .1 Some important features of water

30910 .6 .2 A model for hydrophilicity

30910 .6 .3 The dimensions of hydrophilicity

31010 .6 .4 Rationalizing the structure-hydrophilicity correlation s

using the hydrophilicity model

31 110 .6 .5 Summary

31 610 .7 The structural evolution of hydrophilicity

31 710 .7 .1 The consequences of proton gain

31 810 .7 .2 The consequences of proton loss

31 810 .7 .2 .1 Influence of the basicity of anionic surfactant s

on phase behavior

31 910 .7 .2 .2 Attenuating the basicity of anionic groups

32 110 .7 .3 The limits to hydrophilicity

32 210 .8 Phase behavior as a sensitive indicator of hydrophilicity

324References

324

Chapter II Lipophilicity, remote substituent effects, and HLB

32811 .1 Introduction

32 811 .2 The extensive variation of lipophilicity

32811 .2 .1 Lipophilicity, surface activity, and phase equilibria

33011 .3 Structural variations among hydrocarbon lipophilic groups

33 311 .3 .1 The influence of chain-length

33 311 .3 .1 .1 Hydrotropes

33 811 .3 .2 The structural variation of hydrocarbon lipophilic groups

33 911 .3 .2 .1 Insertion of aromatic rings

33 911 .3 .2 .2 Branching via hydrophilic group position

33 911 .3 .2 .3 Branching via multiple lipophilic groups

34 111 .3 .2 .4 Sodium sulfosuccinate diesters (Aerosols)

34211 .3 .2 .5 Unsaturation

34 311 .3 .2 .6 Alkyl substituents

34711 .3 .2 .7 The biological polar lipid surfactants

34 811 .3 .2 .8 Remote polar substituents

35 211 .4 HLB : hydrophilic-lipophilic balance

35411 .4 .1 Scaling HLB

35411 .4 .2 HLB and pivotal phase behavior

35 511 .5 The intensive variation of lipophilicity

35 511 .5 .1 Fluorocarbon lipophilic groups

35 511 .5 .2 Silicone lipophilic groups

35 911 .5 .3 Polyether lipophilic groups

36 111 .5 .4 Polyester lipophilic groups

36211 .5 .5 Polynitrile lipophobic/hydrophobic groups

36 3References

36 3

Chapter 12 The influence of third components on aqueous surfactant phas ebehavior

36812 .1 Fundamentals of ternary phase science

36 812 .1 .1 Ternary diagrams

36912 .1 .1 .1 Reading compositions

36912 .1 .1 .2 Isotherms and isopleths

37 112 .1 .1 .3 Loci of compositions

37 112 .1 .1 .4 Tie-lines in two-phase mixtures

37 312 .1 .1 .5 Tie-triangles and three-phase mixtures

37 312 .1 .1 .6 Phase ratios and the lever rule in ternary diagrams

37 312 .1 .2 The Phase Rule in ternary systems

37 512 .2 The influence of electrolytes

37 712 .2 .1 The sodium palmitate-sodium chloride-water system

37 712 .2 .2 The alternation rule and Schreinemakers' Rule

38 112 .2 .3 The influence of temperature on sodium palmitate- -

salt-water phase behavior

38 112 .2 .4 The effects of other salts

38 212 .3 The influence of nonpolar oils

38 312 .3 .1 Soap-nonpolar oil-water systems

38 312 .3 .2 Cationic surfactant-nonpolar oil-water systems

38 512 .3 .3 The C IO E4-hexadecane-water system

387

12 .3 .4 The C 8 E4-heptane-water system

39 412 .3 .5 Miscellaneous nonionic-oil-water systems

39 612 .4 The influence of amphiphilic oils

39 612 .4 .1 Soap-medium-chain alcohol-water systems

39 712 .4 .2 Soap-short-chain alcohol-water systems

40 012 .4 .3 Soap-long-chain alcohol-water systems

40 112 .4 .4 Other ionic surfactant-fatty alcohol-water systems

40 112 .4 .5 Nonionic surfactant-fatty alcohol-water systems

40 312 .4 .6 Soap-fatty acid-water systems

40 512 .4 .7 Nonionic surfactant-fatty acid-water system

40 612 .5 The general influence of nonsurfactant third components

40 712 .5 .1 Miscibility within the limiting binary systems

40 712 .5 .2 An overview

40 812 .5 .3 The transition from conditions of surfactant-water

miscibility to surfactant-water immiscibility in surfactant -oil-water systems

40912 .5 .4 The influence of amphiphilic structure in the oil

41 112 .6 The influence of another surfactant

41 112 .6 .1 Homologs

41 112 .6 .2 The octylammonium chloride-octylamine-water system

41212 .7 Summary

41 3References

414

Part V MISCELLANEOU S

Chapter 13 The relationship of the physical science of surfactants to their utility 41 913 .1 "Nondurable goods", "products ", "technologies", and other

terms

41 913 .2 The roles of industrial technologists

42013 .3 Raw material selection : correlating molecular structure with

sales

42 113 .3 .1 The concept of "utility"

42213 .3 .2 Rational, empirical, direct, and indirect correlations

42 313 .3 .3 The concepts of "performance " and "performance data"

42613 .3 .4 The concept of "performance-determining properties "

42713 .3 .5 The characteristics of performance-determining

properties

42813 .3 .5 .1 Performance related to smell and taste

42913 .3 .5 .2 Performance related to seeing, feeling, an d

hearing

42913 .3 .6 The role of phase science in the raw material selection

process

43 113 .3 .6 .1 Rheology

43 113 .3 .6 .2 Optics

43213 .3 .6 .3 Acoustics

43213 .3 .6 .4 Colloidal phenomena

43 313 .3 .6 .5 Solubilization

43413 .3 .6 .6 The role of structural information

434

13 .4 Raw material integration: correlating process variables wit hphase behavior

43513 .4 .1 The process path

43 513 .4 .2 Simplification of the analysis

43613 .4 .3 The reintroduction of complexity

43 713 .4 .4 The various roles of phase behavior in manufacturin g

processes

43 713 .4 .5 The formation of colloidal structure by phase reactions

43 813 .5 Some roles of phase science in medicine

43 813 .6 Summary

439References

43 9

Chapter 14 A history of surfactant phase science

44 114 .1 The pre-Phase Rule era, and the Phase Rule

44 114 .2 Friedrich Krafft (1852-1923)

44214 .3 James William McBain (1882-1953)

44214 .4 The soap-boiling process

44814 .5 Jack Henry Schulman (1904-1967)

45 114 .6 Per Ekwall (1895-1990)

45214 .7 Beyond soaps

45514 .8 The microemulsion studies

45714 .9 Summary

45 8References

459

APPENDICE S

Appendix 1 Glossary and definitions of acronyms and thermodynamic symbols

465A1 .1 A glossary of surfactant phase science terms

465A1 .2 Acronyms used in the text

476A1 .3 Thermodynamic symbols used in the text

47 8

Appendix 2 Literature references to binary and ternary phase studies

480A2.1 Introduction

480A2.2 Binary systems

48 1Ionic class

48 1Anionic subclass

48 1Miscellaneous

484Cationic subclass

484Nonionic class

485Zwitterionic subclass

48 5Semipolar subclass

486Single bond subclass

48 8Miscellaneous

49 1Binary nonsurfactant systems

492A2.3 Ternary systems

493Ionic class

493Dominant surfctant-anionic

493Dominant surfactant-cationic

498

Nonionic class

500Dominant surfactant-semipolar

500Dominant surfactant-single bond

500Nonsurfactant ternary systems

50 3Nonionic compounds

50 3References

50 5

Appendix 3 Extracting, graphing, and using data from published diagrams

509A3.1 Binary diagrams

509A3 .1 .1 Digitizing the diagram

510A3 .1 .2 Graphing the data

510A3 .1 .3 Adding inner boundaries

51 1A3 .1 .4 Miscellaneous curves

51 3A3.2 Ternary diagrams

514A3 .2 .1 Interchanging composition and x, y-coordinate data

514A3 .2 .2 Tie-line calculations in biphasic mixtures

516A3 .2 .3 Phase ratios in tie-triangles

51 7References

520

Appendix 4 The determination of phase diagrams

521A4.1 An approach to the determination of phase diagrams

52 1A4.2 The purity issue

522A4.3 Unary systems

52 3A4.4 Multicomponent aqueous systems

52 5A4.4.1 Crystal hydrates

525A4.4.2 Isothermal analytic methods

526A4.4.3 Isoplethal methods

528A4.4.4 Isothermal swelling methods

53 5A4.5 A comparative evaluation of phase study methods

53 8A4.6 Evaluating the quality of phase diagrams

54 1References

544

Index

547