2002 14sis barcelona salager - firp.ula.ve · it is the ability of a surfactant to produce a...

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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


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


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


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)


Formulation scan (e.g., salinity, EON, temperature)

Optimum Formulation(3 phase behavior)


Solubilization Parameters

Maximum Solubilization at crossingIn Microemulsion at Optimum Formulation

SP water in m SP oil in m

3 φ

Formulation Scan

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Scriven S., Nature 263: 123 (1976)

Bicontinuous Structureswith zero curvature


Winsorʼs R Ratio

Maximum Solubilization when N = D

R = =Aco - Aoo ... NAcw - Aww ... D

R = 1 = = = 2 5 10 2 5 10

is it the same thing?

but ....


Winsorʼs Premise

higher interactionshigher N (or D)higher solubilization

R = 1 = = = 2 5 10 2 5 10

Winsor P., Solvent Properties of Amphiphilic Compounds, Butterworth, London (1954)


Solubilization increases

But, when chain reaches 18-20 carbon atoms,the surfactant precipitates (Krafft Temperature)

Bourrel M., Chambu C., The Rules for Achieving High Solubilization of brine and oil byAmphiphilic Molecules. Soc. Petroleum Eng. J., 23 : 327 (1983)


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


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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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


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)


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


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


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*


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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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)


10.80.60.40.204

5

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


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


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)


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


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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Hydrophilic Linker

SO3Na

SO3Na

H3C-CH2 -CH2 -CH2

H3C-CH2 -CH2 -CH2

Naphtalene Sulfonate= hydrotrope

Di-butyl Naphtalene Sulfonate= hydrophilic surfactant

SO3Na

H3C

SO3Na

H3C

H3C

Mono/Dimethyl Naphtalene Sulfonate= hydrophilic linker


Lipophilic and Hydrophilic Linkers

Adsorbed Surfactant

Lipohilic Linker

Hydrophilic Linker

Oil

Water

Result in :

Better match

(oil does notcontact water)

Smoothervariation ofpolarity


Go thru combo L-H Linker

Capacity of anchoringon both sides with di-block low MW polymers

If a small amount thereis no solubility problem

Solubilization increasecan be large

Jacobs B. et al., Amphiphilic block copolymers as efficiency boosters for microemulsions,Langmuir 15, 6707 (1999)

LL effect

HL effect

attachedpoint atinterface


Smooth Transition at interface pays off

As a corollary, good matching on both sides pays off


... the same effect could be attained with a singlemolecule : “extended” surfactant

Surfactant+ Lipophilic

Linker

hydrophilicgroup

hydrophobicchain

POLY-PROPYLENE

OXIDE

Spacer arm ishydrophobic but

slightly polar, e.g.


Extended Surfactants(1rst Generation)

alkyl

poly-propylene oxide

ethoxy (2-3 EO)

sulfate sodium salt

Miñana-Pérez M. et al. Solubilization of Polar oils in Microemulsion Systems,Progress Colloid Polymer Science, 98 : 177 (1995)

( = lipophilic linker )

( = hydrophilic linker )

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Produce a highSOLUBILIZATION

particularly withnatural oils

PROPYLENE OXIDE NUMBER14106

WOR = 1 T = 35 °C 1.25 wt.% extended Surfactants

Mygyol 812

Soja oil

HexadecaneEthyl Oleate

10

20

30

40

0

SP (ml/g)

Soja oil = natural

triglyceride

Extended Surfactants

Miñana-Pérez M. et al. Solubilization of Polar Oils with Extended Surfactants,Colloids Surfaces A 100 : 217 (1995).


Potential Applications Single phase water-oil mixtures

bladder stone dissolution single phase dressing vegetable oil extraction environmental remediation

Microemulsions for injections (most pharmaceutical products are oil soluble)

Soak-only Detergent Formulation (no stirring required)


Lipophilic-Hydrophilic Linker matching Combo Go thru LHL combined molecule Chlorinated, triglyceride... oil matching New generation of extended ...


2 nd Generation of extended surfactantsfor biocompatible applications

sugarpolargroup

Fatty acid derivative(hydrophobic tail)

LHL tayloredspacer arm

Physico-chemicalProperties of theseProducts are under study

Goethals et al., Spacer Arm influence on Glucido-amphiphilicCompound Properties, Carbohydrate Polymers, 45 : 147 (2001)


Polar heads (simple or combined)currently synthesized and tested in Lab. FIRP

sulfateethoxy-sulfatecarboxylateethoxy-carboxylateC6 sugarsxylitol (C5 sugar)di-xylitolethoxy-xylitolcarboxylate & xylitolcarboxylate & glucose...Good preliminary results

SP > 40 ml/g for hydrocarbonsSP > 10 ml/g for triglicerides


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2002 14sis barcelona salager - firp.ula.ve · it is the ability of a surfactant to produce a...

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