Importance of molecular packing at interfaces as well as in pre-micellar and micellar aggregates for controlling various technological processes

187 Pages·2002·7.4 MB·English

by  Kanicky, James Rene

IMPORTANCEOFMOLECULARPACKINGATINTERFACESASWELLASIN
PRE-MICELLARANDMICELLARAGGREGATESFORCONTROLLING
VARIOUSTECHNOLOGICALPROCESSES
By
JAMESRENEKAN1CKY
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2002
Idedicatethisdissertationtomyparents,whohavewaited
solongtoseemegetarealjob!
ACKNOWLEDGMENTS
I would liketo express my sinceregratitude and appreciation to my advisor.
Professor Dinesh 0. Shah, chairman ofmy supervisory committee, for hisguidance,
enthusiasm, and motivation throughout my career at the University ofFlorida. His
philosophicallessonsonlifeandhappinesshavebeenofgreatinspirationtome. Iam
alsoverythankfultomyothergraduatecommitteemembers.ProfessorsBrij Moudgil,
GarHoflund,andAnujChauhanfortheirvaluabletimeandsuggestions,andtotheUF
DepartmentofChemicalEngineeringfortheirkindsupport.
IwishtothankmycolleaguesfromtheDepartmentofChemicalEngineeringand
theCenterforSurfaceScienceandEngineeringfortheirhelpandcooperation: Dr.Alex
Patist, Dr. PeterKang,Dr. SteveTruesdail, Dr. ByronPalla, Dr. P. K. Patanjali,Dr.
Brajesh Jha, Dr. Dibakar Dhara, Dr. Rahul Bagwe, Juan-Carlos Lopez-Montilla, Dr.
TapanJain,SamirPandey,Dr.ManojVarshney,andMonicaJames. Iwouldalsoliketo
thankallofmyundergraduatestudentassistants,especiallyAdamPoniatowski,fortheir
experimentalcontributionstothisthesis.
IwouldalsoliketoexpressmygratitudetoProf.KristerHolmbergforproviding
mewithGeminisurfactantsamples,andtotheEngineeringResearchCenter(ERC)for
ParticleScienceandTechnologyattheUniversityofFloridaforsponsoringmyresearch
aswell asfortrainingmeformynewcareerin industry. I alsowishtothankERC
colleagueDr.YakovRabinovichforhishelpwiththeAFMmeasurements,aswellasDr.
JoshuaAdler,Dr.PankajSingh,Dr.BaharBasim,MadhavanEsayanur,andScottBrown
111
for their help with various aspects of my research and for very enlightening
conversations.
Finally,butmostimportantly,myheartfeltgratitudegoestoElkeMichalak,who
hasbroughtnewmeaningtomylife,andtomyparents,Anne-MarieandJamesKanicky,
towhomIoweeverything.
IV
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
iii
LISTOFTABLES viii
LISTOFFIGURES ix
ABSTRACT xvi
CHAPTER
INTRODUCTION
1 1
1.1 Surfactants 1
1.2 SurfactantAdsorption 4
1.3 Micellization 6
1.4 StructureofaMicelle 9
1.5 DynamicPropertiesofSurfactantSolutions 13
1.6 ImportanceofMicellarRelaxationTimeonTechnologicalProcesses....26
1.7 Long-ChainFattyAcidsandSoaps 35
1.8 RationaleoftheProposedResearch 44
2 DETERMINATIONOFFATTYACIDpHFOROPTIMAL
PERFORMANCEINVARIOUSINTERFACIALPHENOMENA 47
2.1 Introduction 47
2.2 MaterialsandMethods 49
2.3 EffectofpHonPerformanceofFattyAcidinVarious
InterfacialPhenomena 55
2.4 EffectofChainLengthonFattyAcidpKa 67
2.5 Conclusions 70
v
3 EFFECTOFCHAINLENGTHCOMPATIBILITYANDDEGREEOF
UNSATURATIONONTHEpKaOFLONG-CHAINFATTY
ACIDSOAPS 71
3.1 Introduction 71
3.2 MaterialsandMethods 74
3.3 EffectofDegreeofUnsaturationonpKa 75
3.4 EffectofChainLengthCompatibilityonpKaofMixedFatty
AcidSolutions 81
3.5 Conclusons 84
4 EFFECTOFPREMICELLARAGGREGATIONONTHEpKaOF
FATTYACIDSOAPSOLUTIONS 86
4.1 Introduction 86
4.2 MaterialsandMethods 87
4.3 EffectofChainLengthonpKa 87
4.4 EffectofSurfactantConcentrationonpKa 90
4.5 Conclusions 92
5 KINETICSOFGEMINIANDMIXEDSURFACTANTMICELLES 94
5.1 Introduction 94
5.2 MethodstoMeasureMicelleStability 96
5.3 MaterialsandMethods 102
5.4 KineticsofMicelleswithAddedFattyAcid 104
5.5 KineticsofMixedSurfactantMicelles 109
5.6 KineticsofGeminiSurfactantMicelles 110
5.7 Conclusions 119
6 CORRELATIONOFPARTICULATEDISPERSIONSTABILITY
WITHTHESTRENGTHOFSELF-ASSEMBLEDGEMINI
SURFACTANTFILMS 120
6.1 Introduction 120
6.2 MaterialsandMethods 126
6.3 StructuresofGeminiSurfactantMicellesAdsorbedatthe
Solid/LiquidInterface 128
6.4 Conclusions 133
vi
7 SUMMARYANDRECOMMENDATIONSFORFUTUREWORK 135
7.1 EffectofpHonMolecularInteractionsofLong-ChainFattyAcids 135
7.2 EffectofChainLengthCompatibilityandDegreeof
UnsaturationonFattyAcidpKa 135
7.3 EffectofPremicellarAggregationonFattyAcidpKa 136
7.4 KineticsofMixedandGeminiMicelles 136
7.5 DispersionofParticlesUsingGeminiSurfactants 137
7.6 RecommendationsforFutureWork 138
7.7 Publications 141
APPENDICES
A DETERMINATIONOFAREA/MOLECULEOFANADSORBED
SURFACTANTMONOLAYERUSINGTHEGIBBS
ADSORPTIONISOTHERM 142
B AREA/MOLECULECALCULATIONSOFVARIOUSGEMINI
SURFACTANTS 149
C CALCULATIONOFGEMINISURFACTANTMONOLAYER
DESORPTIONRATES 153
REFERENCES
156
BIOGRAPHICALSKETCH 168
Vll
LISTOFTABLES
Table page
21--1 Physicalpropertiesofselectedfattyacids 37
32--1 pKavaluesofselectedcarboxylicacids 49
2-2 CalculatedparametersofGibbsadsorptionequationusedindetermination
ofarea/moleculeof0.05wt%sodiumlauratesolutionvs.pH 66
3 ComparisonbetweenexperimentallydeterminedpKavaluesandobserved
phenomenaforfattyacidsaltsof(C8-Ci6)chainlengths 69
1 SelectedphysicalpropertiesofC!8fattyacids 80
5-1 Comparisonofexperimentalandliteraturevaluesof12-2-12,12-3-12,
and12-4-12Geminisurfactantcmc 113
5-2 Equilibriumsurfacetension,initialdesorptionrate,andequilibrationtime
ofC12TABandvariousGeminisurfactants 117
B-l Tabulatedvaluesofareapermoleculeandintermoleculardistanceof
12-2-12,12-3-12,and12-4-12quaternaryammoniumbromide
Geminisurfactantsadsorbedattheair/waterinterfaceatconcentrations
belowcmc(C~1mM) 152
viii
LISTOFFIGURES
Figure page
1-1 Schematicrepresentationofatypicalsurfactantmolecule 1
1-2 Effectoftotalsurfactantconcentrationontheconcentrationsofspecies
presentinsolution 7
1-3 Schematicrepresentationofthepossiblestatesinwhichasurfactant
monomercanexistinwater(freemonomers,anadsorbedlayer
attheair/waterorsolid/waterinterface,andmicelles) 8
1-4 Severalofthedifferenttypesofmicellarshapesencounteredina
surfactantsolution 12
1-5 Packingparameteranditsrelationtomicellestructure 14
1-6 Mechsoalnuitisomnsafboorvtehecmtwcorelaxationtimes,nandx2,forasurfactant 15
1-7 Typicalsizedistributioncurveofaggregatesinamicellarsolutionaccording
totheAniannson-Wallmodelofstep-wisemicellarassociation. Region
(I)correspondstomonomersandoligomers;Region(III)toabundant
micelleswithaGaussiandistributionaroundthemeanaggregation
number,W;andRegion(II)totheconnecting“wire”(heattransfer
analogy)or“tube”(masstransferanalogy)betweenRegions(I)and(III) 16
1-8 Schematicrepresentationofthetwopossiblereactionpathsforthe
formationofmicelles(a),andthecorrespondingresistances(b).
(1)Formationbyincorporationofmonomers(Equation1.8);
(2)Formationbyreversecoagulationofsubmicellaraggregates
(Equation1.13) 21
1-9 Schematicrepresentationofadsorptionofsurfactantontothenewly
createdair/waterinterfaceduetodisintegrationofmicellesduring
foamgeneration 28
1-10 Schematicrepresentationofadsorptionofsurfactantontofabricdueto
disintegrationofmicellesduringwetting 29
IX
1-11 Schematicdiagramfortheadsorptionofsurfactantmonomersfromthe
bulktotheoil/waterinterfaceduringemulsification 30
1-12 Theslowrelaxationtime,X2,ofSDSmicellesatvarioussurfactant
concentrations 31
1-13 SchemmaMtiScDdSiacgornacmesntsrhatoiwoinngmicellarpackingat50,100,200and250 32
1-14 Liquid/gasinterfacialphenomenaexhibitingminimaandmaximaat200mM
SDSconcentration 34
1-15 Liquid/liquidandsolid/liquidinterfacialphenomenaexhibitingminimaand
1- maximaat200mMSDSconcentration 35
1-16 Molecularstateoffattyacidbelowcmcinaqueoussolution 40
2-
1-17 Speciesdistributionofpotassiumoleate(3x10'5M)asafunctionofpH 41
1-18 Speciesdistributionofpotassiumoleate(3x10'5M)asafunctionofpH
usingdifferentestimatesofthermodynamicconstantsthanin
Figure1-17. TheR2H'curveisadashedline 43
19 Flowchartillustratinghowprinciplesofmicellekineticscanbecombined
withfattyacidadsorptionstudiesinordertotailorthekineticsofa
micelle. Gray-filledboxesindicatethescopeofthisdissertation 45
1 Setupforthemeasurementofdynamicsurfacetensionbythemaximum
bubblepressuremethod 51
2-2 Schematicdiagramoffoamcolumnusedforfoamabilityandfoam
stabilitystudies 53
2-3 Schematicdiagramoftheexperimentalsetupforevaporation
measurements. ThedessicantusedwasCaCU 54
2-4 Surfacetension(y)vs.pHof0.05wt%sodiumlauratesolution 57
2-5 Dynamicsurfacetension(DST,2seclifetime)andequilibriumsurface
tensionmeasurementsfor0.05wt%sodiumlauratesolutionvs.pH 57
2-6 Foamheightof0.05wt%sodiumlauratesolutionvs.pHinfoamcolumn
preparedbysingle-capillaryinjectionofair 58
2-7 Maximumfoamstabilityof0.05wt%sodiumlauratesolutionvs.pHin
foamcolumnpreparedbysingle-capillaryinjectionofair 59
x