Chapter 3 Solution of Surfactants

1
Chapter 3 Solutionof Surfactants

• Micelle Formation Applications

2006.3.28.
2
1 Solution Properties of Surfactants and CMC

• Changes in some physical properties of an aqueous
  solution of surfactants in the neighborhood of
  CMC
• such as sodium dodecyl sulfate

3

• 2. Micelle Formation and CMC
• Definition the concentration at which this
  phenomenon occurs is called the critical micelle
  concentration (CMC)
• Formation mechanism
• Iceberg structure ?S?or ?G?H-T?S?
• Surface activity
• Adsorption at interface or surface
• Formation micelle in solution phase

4

• (3) Determination
• Electrical conductivity
• Molar (Equivalent) conductivity(????)
• Surface tension
• Light scattering
• Refractive index
• Colligative property (osmotic pressure)
• Unit mole/L or g/L
• Ionics 10-2 - 10-3 mole/L
• Nonionics 10-3 - 10-6 mole/L

5

• 3. Thermodynamics of micellization
• Mass action model
• (a) Equilibrium constant K
• e.g. anionics n anions, m counter ion
• micelle charge z n-m
• nR- mM ? MmRn-(micelle)
• K FMmRn-/R-n Mm
• F fMR/fRnfMm
• Dilute solution K MmRn-/R-n Mm
• 
  MmRn-/R-n Mn-z

6

• (b) Stantard Free Energy of micellization
• ?Gºm -(1/n)RTlnK
• -(1/n)RTlnMmRn-/R-n
  Mn-z
• RTln R- M(n-z)/n
• R-?MCMC
• ?Gºm RTlnCMC2-z/n
• (2-z/n)RTlnCMC
• If z0 then nm no surface charge
• ?Gºm 2RTlnCMC
• If zn then no counter ion
• ?Gºm RTlnCMC

7

• unitCMC(mole/L) mole fraction
• ?G? RTlnXCMC RTlnCMC/(1000/18)
• RTlnCMC/55.5
• (c) Nonionics nR ? Rn
• k FRn/Rn ?
  Rn/Rn
• ?Gºm -(1/n)RTlnK
• RTlnR RTlnCMC
• ?G? RTlnXCMC RTlnCMC/(1000/18)
• RTlnCMC/55.5

8

• (2) Phase separation model
• (pseudo phase??)
• ?m ?2
• Pseudo phase ?m ?m0 (pure phase)
• Solution ?2 ?20 RTlna2
• ?Gºm ?m- ?20 RTlna2
• 1-1type a2aa- a2
• ?Gºm 2RTlna
• 2RTln(CMC/55.5)

9

• 4. Micellar Structure and Shape
• Structure of Micelle
• Ionics
• inner core - liquid phase hydrocarbon
• Shell
• diffuse electric double layer
• (b) Nonionics
• inner core - liquid phase hydrocarbon
• Shell

Ionics Nonionics
10

• (2) Structure of Reversed Micelle(???)
• In Polar Solvent few no micelle formation
• In Nonpolar Solvent a few small micelle
  formation
• Hydrophilic groups
• Anionicsgtcationicsgtnonionics
• Hydrophobic groups
• R ? reversed micellization?

11

• (3) Micelle Shape dependent of concentration
• (4) Micellar Aggregation numbers(n)
• ( )TP CCMC 10CMC n is independent of
  concentration. c ?, numbers of micelle?
• nionics 50 60 nnonionics gt 400

12

• (c) Factors affecting the n value
• Hydrophobic groups
• hydrophobicity(R, or SiR or FR)?, n ?
• Hydrophilic groups
• Nonionics gt Ionics (same R)
• Electrolyte , Ionic Strength I(1/2)?CiZi2 ?,
  ionics,
• hydrophilicity ? , surface activity ?,
• the radius of ionic atmosphere ?, n?

13

• Regulator of water structure(??????)
• Promoters ? fructose,xylose n?
• Breakers ? urea,lower alcohol n?
• Polar organic compound
• such as solubilization longchain polar organic
  compound n ?
• Temperature if T?, then
• Ionics water-soluble?, n?
• Nonionics water-soluble?, n?.
• Difference between surfactants solvents?, n?

14
(No Transcript)
15
(No Transcript)
16

• 5. Critical Micelle Concentration(CMC)
• Mensuration of CMC
• Surface tension - ?logc, error 2-3
• Electric conductance (???)
• Molar conductance ? ?0 ?c1/2
• Conductance(???) ? logc
• (c) Light scattling(???)
• (d) Dyeing (???)
• (e) Solubilization (???)

17

• (2)Factors affecting CMC
• Structure of surfactants
• Hydrophobic groups
• Fluorocarbons lt Silicones lt Hydrocarbon lt
  Branched Hydrocarbon
• Rn logCMC A B n
• (ionicsn8-18 nonionicsn?12)
• Parameter A ionicsA1.4-1.6
• nonionicsA2-2.4.
• Parameter B ionicsB0.3
• nonionicsB0.5

18

• Branching degree ?, to loosely packed,
• CMC ?
• Position of polar groups end?middle,
• CMC ?
• Unsaturation polar groups
• hydrophilicity ?, CMC ?
• Hydrophilic groups
• ionics nonionics 1-2 orders of magnitude
• polarity?, CMC?
• RCOO gt RSO3 gt RSO4

19

• The Counterion in Ionics
• the CMC in aq. reflects the degree of binding of
  the counterion to the micelle.
• Increased binding of the counterion, in aq. cases
  a decrease in the CMC of surfactants.
• The extent of binding of the counterion increases
  with increases in its polarizability and
  valence(???), and decreases with increases in its
  hydrated radius(????)

20

• e.g. anionic lauryl sulfates
• LigtNagtKgtCsgtN(CH3)4gtN(C2H5)4 gtCa2, Mg2, in
  particular RNH3, R ? CMC?
• Cationic quaternary ammonium salt
• F-gtCl-gtBr-gtI- ,CMC?
• The degree of binding of the counterion(DBC) to
  the micelle depends on the surface charge density
  of the micelle.
• charge? or surface area?, DBC?, CMC ?
• R(CH3)3Br, R ?, tighter packing, DBC?, CMC?

21

• (b) Temperature
• Ionics T ?, CMC ?
• Nonionics T ?, CMC?
• (c) Additives
• Ionic Strength I(1/2)?CiZi ?, hydrophilicity ?
  , surface activity ?, CMC ?
• Electrolyte Anionics Cationics gt
• Zwitterionics gt Nonionics
• AC logCMC -alogCi b (Ci-total
• counterion
  concentration)

22

• Anionics PO43-gtB4O72-gtOH-gtCO3-gtHCO3-gt
• SO42-gtNO3-gtCl-
• ZN logCMC -KCs constant
• Cs- concentration of electrolyte (mole/L)
• Regulator of water structure(??????)
• Promoters ? fructose,xylose CMC ?
• Breakers ? urea,lower alcohol CMC ?
• Polar organic compounds
• Short Chain lower affect
• Long Chain synergism (????)

23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32

• (3) Factors affecting the CMC/C20
• Ionics (C10-C16) R?, CMC/C20 ?
• Branching degree ? , CMC/C20 ?
• Polar hydrophilic head ? , CMC/C20 ?
• Ionic strength ?, CMC/C20 ?
• T(10-40ºC) ?, CMC/C20 ?
• Fluorocarbons gt Silicones gtHydrocarbon
• Saturated aliphatic hydrocarbon-water interface
  CMC/C20 ? then G-Water
• (h) unsaturated aliphatic hydrocarbon or short
  chain aromatic hydrocarbon -water interface
  CMC/C20 ? then G-Water
• (i) PEO nonionics gt zwitterionics gt ionics

33
(No Transcript)
34
(No Transcript)
35
2. Surfaceactivity in Mixtures of Surfactants

• Two important works in researches and
  exploitation of surfactants
• Relation between structure of surfactants and
  properties
• Molecular design synthesization of new
  surfactants
• Application exploitation according to structure
  of surfactants
• (2) Synergism in mixtures of surfactants
• Composite

36

• 2. Adsorption of surfactant mixtures (N
  surfactants)
• Surface excess concentration ?i of i component
• mixtures -(d?/RT) ? ?i dlnCi
• if other j components Cj constant
• then dCj dlnCj 0
• -(d?/RT) ?i (dlnCi)T,P,nj
• ?i -(1/RT)d?/dlnCiT,P,nj
• ?i is measurable. d?/dlnCiT,P,nj mean that the
  rate of change between surface tension of
  solution and dlnCi when the concentration of
  other j components are constant.
• Ionics ?i -(1/xRT)d?/dlnCiT,P,nj

37

• (2) Adsorption isotherm of surfactant mixtures
• e.q. two surfactants component 1 2
• Rate of adsorptiondna1/dt ka1(?? - ?1 - ?2 )C1
• Rate of desorption dnd1/dt kd1?1
• Adsorption equilibrium
• Rate of adsorption Rate of desorption
• ka1(?? - ?1 - ?2 )C1 kd1?1
• If k1 ka1/kd1,then
• ?1 (1k1C1) k1C1(?? - ?2 )
  ?
• Same ?2 (1k2C2) k2C2(?? - ?1 )
  ?

38

• ?? ?1(1k1C1) ?2(1k2C2)
• k1C1(?? - ?2 ) k2C2(?? - ?1
  )
• ?? (k1C1 k2C2) - ?2k1C1?1k2C2
• (?1 ?2)(1k1C1k2C2) ?? (k1C1 k2C2)
• ? (?1 ?2) ?? (k1C1 k2C2)/(1k1C1k2C2)
• ?? ?kiCi/(1 ? kiCi)
• ?i ?? kiCi/(1 ? kiCi)
• If Xi the molar fraction of I component, Ci and C
  the concentration i and total component
• Then Ci XiC, ?i ?? CkiXi/(1 ?CkiXi)
• ?i ?? CkiXi/(1 C? kiXi)

39

• If K ? kiXi, then ?i ?? CkiXi/(1 C? kiXi)
• ?? CkiXi/(1
  CK)
• ? ??i ?? C?kiXi/(1 CK)
• ?? CK/(1 CK)
• 3. Micelle formation of surfactant mixtures (N
  surfactants)
• Ideal mixed micelle formation of surfactant
  mixtures surfactant homologous mixtures
• The surfactant solution is ideal
• The mixed micelle is ideal solution
• The interaction of i component in pure or mixed
  micelle

40

• Phase separation model
• (pseudo phase??)
• chemical potential of i component
• (micelle) ?mi ?i (solution)
• Pseudo phase ?mi ?mi0 RTlnXmi
• Solution ?i ?i0 RTlnCTXi
• RTlnCTXi (?mi- ?i0) RTlnXmi
• lnCTXi A-K0ln(CTCS) RTlnXmi
  ? K0 Constant about electric work
  
• Cs Concentration of salt
• In pure i component micelle solution
• lnCi A-K0ln(CiCS)
  ?

41

• ? - ? ln(CiXmi)/(CTXi) ln(CTCS)/(CiCS)K0
• Xmi/Xi CT(CTCS)/Ci(CiCS)K0
• Xmi Xi CT(CTCS)/Ci(CiCS)K0
  ? ??Xmi 1,? from ?
• ?CT(CTCs)k0/Ci(CiCs)k0 Xi 1
• ? Xi /Ci(CiCs)k0 1/CT(CTCs)k0
  ?
• ??Xi 1,? from ?
• ? XmiCi(CiCs)k0 CT(CTCs)k0
  ?
• CT CMC CMC of mixed micelle
• Ci CMCiº - CMC of i pure component

42

• ?1/CMC(CMCCs)k0? Xi /CMCºi(CMCºiCs)k0
• ?CMC(CMCCs)k0 ? XmiCMCºi(CMCºiCs)k0
• 1/CMC(CMCCs)k0? Xi /CMCºi(CMCºiCs)k0
• CMC(CMCCs)k0 ? XmiCMCºi(CMCºiCs)k0
• Discussion
• Nonionics , no electric interaction, K00
• 1/CMC? Xi /CMCºi ,,
• 1/CMC X1 /CMCº1 X2 /CMCº2
• CMC ? XmiCMCºi
• CMC Xm1CMCº1 Xm2CMCº2

43

• Ionics K0?0, if CS 0
• 1/CMC1k0? Xi /CMCºI 1k0
• CMC1k0 ? XmiCMCºi1k0
• If CS ? , CS CT CMC CMCºI
• 1/CMC(CMCCs)k0? Xi /CMCºi(CMCºiCs)k0
• 1/CMC (Cs ) k0? Xi /CMCºi(Cs)k0
• 1/CMC ? Xi /CMCºi
• CMC ? XmiCMCºI
• Same with nonionics

44

• (2) non ideal mixed micelle formation
• e.g. nonionics
• 1/CT?Xi/fiCi
• CT?XmifiCi
• fi the activity coefficient of i component in
  solution
• 3. Synergism(????) in mixtures of surfactants
• Molecular Interaction Parameters (MIP) ?lt 0
• ?? - Molecular Interaction Parameters for mixed
  monolayer formations
• ?? - Molecular Interaction Parameters for mixed
  micelle formations

45

• (2) Effect of chemcal structure and molecular
  environment on MIP
• Effect of various types on ?
• anionic-cationic gt anionic-zwitterionic gt
  ion (anionic, cationic)-POE nonionic gt betaine
  cationic gt betaine - POE nonionic gt POE
  nonionic POE nonionic
• (b) R?, ?? ?? appears to be maximum when
  the lengths R of the two surfactants ?M
  becomes more positive with increase in the total
  number of carbon atoms of two surfactants.

46

• (c) Electrolyte ??
• (d) Temperature ?, ?? (10 - 40C)
• Values of Molecular Interaction Parameters

47
Values of Molecular Interaction Parameters
48
Values of Molecular Interaction Parameters
49
Values of Molecular Interaction Parameters
50
Values of Molecular Interaction Parameters
51
Values of Molecular Interaction Parameters
52
End