1 1 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 J. L. Salager, C. Scorzza, A. Fernández, R. E. Antón, M. Miñana, A. Usubillaga, P. Villa Lab. FIRP University of the Andes Mérida, Venezuela 2 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 What is Solubilization? it is the ability of a surfactant to produce a monophasic system containing both oil and water surfactant (+ alcohol) water oil polyphasic zone monophasic zone “height” of polyphasic zone generally at center S+A 3 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 All phase diagrams contain a monophasic zone If a formulation variable is changed (along a Formulation scan) How solubilization changes? 2! W O S 1! 1! W O S 2! 1! W O S 2! 3! 2! Bourrel M., Schechter R. S., Microemulsions and Related Systems, Marcel Dekker, New York 1988 4 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 The “height” of polyphasic zone at fixed oil/water composition (e.g. 50/50) is monitored lowest “height” = maximum solubilization at optimum formulation “Height” Formulation Scan S + A Bourrel M. et al. The Topology of Phase Boundaries for oil-brine- surfactant Systems ... Soc. Petroleum Eng. J., 22: 28 (1981) 5 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 Formulation scan (e.g., salinity, EON, temperature) Optimum Formulation (3 phase behavior) 6 / 36 14th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002 Solubilization Parameters Maximum Solubilization at crossing In Microemulsion at Optimum Formulation SP water in m SP oil in m 3 φ Formulation Scan
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1 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
J. L. Salager, C. Scorzza, A. Fernández, R. E. Antón,M. Miñana, A. Usubillaga, P. Villa
Lab. FIRP University of the AndesMérida, Venezuela
2 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
What is Solubilization? it is the ability of a surfactant to produce a
monophasic system containing both oil and water
surfactant(+ alcohol)
water oil
polyphasiczone
monophasiczone
“height” ofpolyphasic zone
generally at center
S+A
3 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
All phase diagrams contain amonophasic zone
If a formulation variable is changed (along a Formulation scan) How solubilization changes?
2!W O
S
1! 1!
W O
S
2!1!
W O
S
2!3!2!
Bourrel M., Schechter R. S., Microemulsions and Related Systems,Marcel Dekker, New York 1988
4 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
The “height” of polyphasic zone at fixedoil/water composition (e.g. 50/50) is monitored
lowest “height” = maximum solubilizationat optimum formulation
“Height”Formulation Scan
S + A
Bourrel M. et al. The Topology of Phase Boundaries for oil-brine-surfactant Systems ... Soc. Petroleum Eng. J., 22: 28 (1981)
5 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Bourrel M., Chambu C., The Rules for Achieving High Solubilization of brine and oil byAmphiphilic Molecules. Soc. Petroleum Eng. J., 23 : 327 (1983)
11 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
In some cases Winsorʼs model does notexplain the increase in solubilization
% aditivo en aceite
20
43210
% Additive in oil
10
0
OP 0 EOOP 1 EOOP 1.5 EOOP 3 EO
Additive
SP* ml/g 0.034 M SurfactantEthoxylated Octylphenol(EON near 5)Isooctane, WOR =1, 25ºC
Solu
biliz
atio
n Pa
ram
eter
12 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
It is evidently a new phenomenonthat cannot be interpreted fromWinsorʼs premise !
This is the so-calledLIPOPHILIC LINKEReffect which will beanalyzed next.
Graciaa A. et al. Improving Solubilization in Microemulsions with Additives - Part I :The Lipophilic Linker role, Langmuir 9, 669 (1993)Graciaa A. et al. Improving Solubilization in Microemulsions with Additives - Part II :Long chain Alcohol as Lipophilic Linkers, Langmuir 9, 3371 (1993)Salager J. L. et al. Improving Solubilization in Microemulsions with Additives. Part III:Optimization of the Lipophilic Linker, J. Surfactants Detergents 1, 403 (1998)
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13 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Proposed Mechanism “
orde
red”
zon
e
“ord
ered
” zo
ne
WATER WATER
The Lipophilic Linker increases interactions on the oil sideby “ordering” the molecules deeper inside the oil bulk phase
OILOIL
INTERFACEInterface
LipophilicLinker
14 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
The Lipophilic Linker
does not adsorb at interface (it is not a cosurfactant) is a slightly polar oil (or a very lipophilic amphiphile) is located inside oil phase near interface (interfacial segregation) “stretches” the reach of surfactant in oil (without producing precipitation)
15 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Examples of Lipophilic Linkers
Long chain n-alcohols ( > 8) Long chain alkylphenols ( > 8) idem slightly ethoxylated (EON < 2)
Single chain esters (ethyl oleate)
probably other linear lipophilic amphiphiles
16 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
n-Alcohols as Lipophilic Linkers>>> 8 or more C atoms
EON
SP (m
/g)
02468
10
0 2 4 6 8 10 12 14 164
5
6
Number of Carbon atoms in n-alcohol
Systems: 0.02 M ethoxylated Octylphenols, 0.03 M n-alcohol, T = 25 °C, Isooctane, WOR= 1
Effect
Lipophilic Linker
EffectCosurfactant
Dilutioninterfacial
0 2 4 6 8 10 12 14 16
Lipophilic Linker
CosurfactantEffect
Effect
17 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
0 2 4 6 8 10 12 14 16
0.02 M Ethoxylated Alkylphenol T = 25 °C0.0325 M n-alcohol Isooctane WOR = 1
ALCOHOL CARBON NUMBER
SP (ml/g)
Alcohols as Lipophilic Linkers
LipophilicLinker effectadds up tosurfactanteffect
DODECYL
NONYL
OCTYL
8.3
8.3
8.9
9.4
9.59.5
5.3
5.6
5.6
5.85.8
5.8
5.75.1
5.3
5.75.6
5.3
EON*
18 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
The Lipophilic Linker is ... ... a very lipophilic amphiphile or a polar oil ... ... which acts at very low concentration because it locates itself ... ... near interface
It is not a case of adsorption ... ... but of segregation
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19 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Interfacial Segregation Take an oil mixture... ... (same molar volume oils) Hexadecane --> non polar (ACN = 16) Ethyl Oleate --> polar (EACN = 6)
Measure or evaluate interfacial tension optimum formulation oil composition near interface
Graciaa A. et al., Interfacial Segregation of Ethyl Oleate/Hexadecane OilMixture in Microemulsion Systems, Langmuir 9 : 1473 (1993)
20 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
10.80.60.40.204
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6
ETHYL OLEATE FRACTION in OIL
EON* interfacial
T = 35°C
ETHYL OLEATEHEXADECANE
5 wt % OP+EONWOR = 1
{OIL
(2.2)
(4.2)(4.3)
(3.8)
(4.0)
(3.2)
(2.8)
(1.5)
interfacial SP*
Everything happens asif the “interfacial” oilwere “pure” polar oil,when there is 50% ormore of this oil in themixture (blue arrow)
= polar oilsegregationnear interface
Interfacial Segregation
21 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
10.80.60.40.20
Tension interfacial
Interfacial Segregation
ETHYL OLEATE FRACTION in OIL
Everything happens asif the “interfacial” oilwere “pure” polar oil,when there is 50% ormore of this oil in themixture (blue arrow)
= polar oilsegregationnear interface
ETHYL OLEATEHEXADECANE{Oil
22 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
The LIPOPHILIC LINKER effect is dueto the SEGREGATION of the mostpolar substances in the oil phasewhich concentrate near interface
The other phase and the surfactantonly “see” the most superficiallayer of the oil phase(similar to a chocolate covered candy)
23 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Lipophilic Linker Role
The Lipophilic Linker “stretches” (in situ) ... … the surfactant hydrophobic “tail”
The L.L. produces aslightly polar zoneinside the oil phase,near the interface
24 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002
Hydrophilic Linker Similar role on the water side
Uchiyama H. et al. Supersolubilization in Chlorinated Hydrocarbon Microemulsions.Solubilization Enhanced by Lipophilic and Hydrophilic Linkers, Industrial & EngineeringChemistry Research 39 : 2704 (2000)Acosta E. et al, The Role of Hydrophilic Linkers, J. Surfactants Detergents, 5: 151 (2002)
di-hexyl-sulfoccinate
The H.L. produces aslightly less polar zoneinside the water phase,near the interface
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25 / 3614th Symposium “Surfactants in Solution” SIS2002, Barcelona, Spain June 9-14, 2002