Cosmet, Sd,, 58, 451-476 (July/August2007) Semi-permanentsplit end mendingwith a polyelectrolytecomplex R. RIGOLETTO, Y. ZHOU, and L. FOLTIS, InternationalSpecialty Products, 1361 AlpsRoad,Wayne,N.J. 07470. Synopsis Split endsform throughmechanical stresses duringgroomingprocedures and aremorelikely to appearin hair damagedasa resultof excessive combingforces.Althoughthereare no conventional systemsthat will permanentlymendsplit ends,a semi-permanent mendingcomposition hasbeenachievedthrougha polyelectrolytecomplex.The complexis formed as a result of the ionic association of a cationicpolymer, Polyquaternium-28,and an anionic polymer, PVM/MA Copolymer.Hair tressescontaining tagged split endsareusedin measuring mendingefficacy.The taggingallowsthe fateof the split endsto be determined afterdifferenttypesof treatmentregimenswhichtestthe durabilityof the mend.Monitoringof the repair andmendingdurabilityis carriedout with the aid of a stereomicroscope. Resultsobtainedwith this method indicatethat the complexbothby itselfandwhenformulatedinto a simplelotionprovideda high levelof split end mending not only after initial treatmentbut more importantlyafter combingshowingthe durabilityof the mend.Cumulativeeffectsand durabilityto washingindicatethat the polymercomplex doesnot build up on the hair and rinsesoff with shampoomakingpossibleits usageasa postshampoo treatment.The formulatedlotion hashigherdurabilityperformance ascomparedto a commercialproduct with a split endmendingclaim.The proposed mechanism of actionentailsa crosslinking microgelstructure that infiltratesthe damagedhair sitesbindingthem together.This modelis supportedby the analysisof phasebehavior,viscometry, Scanning ElectronMicroscopy, andabsorption of ionicdyes. INTRODUCTION The manifestationof damagedhair as seen macroscopically as we view whole hair attributes is basedon the state of each of the individual fibers taken collectively. Different typesof damageare observedon a microscopicscaleusing scanningelectron microscopyas a diagnostictool (1). These consistof transversefracturesthrough the hair's cuticle, transversefractures of the whole fiber, delamination within the cuticle, longitudinalsplitting of the hair shaft(split ends),and multiple longitudinalsplitting of the hair shaft (trichorrhexis nodosa) (2). Each of these structural maladies when multiplied by the numberof fibersis portrayedin wholehair attributessuchasdullness, lack of manageabilityor stylability, rough texture,and poor combability.The hair as a whole basedon the stateof the individual fiberslooksunhealthy. There are multiple causesfor this damageand encompass physical,chemical,and environmentalfactors.Versatilityof hair stylesis a majorcauseof the predominance of hair damage.Consumersdesireproductsthat allow them to expresstheir individuality and personalstyleto a greaterextent.Keepingup with the latesthair stylefashionincludes 451 452 JOURNAL OF COSMETIC SCIENCE oxidativehair coloringand permanentwaving.Also styling agentsin combinationwith stylingimplementssuchascurlingandflat ironsallowsoneto havea differenthair style evenfrom oneday to the next. The resultof this increasedamountof styling hasits effect on the quality and conditionof the hair. This is compoundedwith longerhair styles sincethe endsof the hair are older and haveexperiencedmore weatheringaswell as the aggressive stylingtreatments.Eventuallythe hair becomes dull, unmanageable, coarseto the touch,andhardto comb.When viewingthesedamagedfiberson a microscopic scale one realizesthe causeof what is observedon the macroscopic scale.With the predominanceof aggressive styling behaviorsit is clearthat there is a market needfor compositionsand productsthat are able to not just prevent hair damagebut, what is more challenging,affectits repair. One manifestationof damagethat affectswholehair attributesare fibersthat havesplit longitudinally at their tip ends.The technicalterm for split endsis trichoptilosis.The theory of split end formation as proposedby Swift is fully elaboratedin an article entitled Mechanismof split--end formationin human headhair (3) and is depictedin Figure l. A cluethat led to the theoryon the mechanismof split endformationwasfrom an SEM of a split endfiber. It wasobserved that the split occurredin sucha mannerthat it formedparallelto the majoraxisof the hair diameter(4). Swift theorizedthat when hair is combedthe elliptically shapedhair fiberspreferentiallyorientaresso that the majoraxisis parallelto the surfaceof the combtooth. As the combtraverses the hair, shearstresses are producedparalleland longitudinalto the major axisof the fiber. The degreeof shearstressis distributedparabolicallyalongthe minor axisof the hair sothat the shearplane sufferingthe most shearstresswould be that running parallel to the major axisof the hair. When the shearforcebecomesgreat enoughtiny fracturesoccur along this axis and eventuallywill propagateto the end of the fiber. As the comb is pulled through the hair the bending is propagatedfrom root to tip; it is not a static bend.As the combreachesthe tip end of the tressthe collectionof fiberstend to snarl increasingthe shearstresses to a greaterextent at the tip than anywhereelsealong the fiber length. Fibersare dynamicallybent over 180 degreesas observedundera stereo- Comb tooth Major diameter Shear stress y axis Figure 1. Mechanismof split end formationshowingthe distributionof shearstresses in fiber during combing.Depictionof theoryproposedby Swift (3) 2006 TRI/PRINCETON CONFERENCE 453 microscope (Figure2). The major stressthen leadingto hair fractureis not just oneof stretchingsuchas is measuredby tensilestrength,but ratherflexureor bending(5). Combing,then, is the major route that fiberstend to split sincetheseshearforcesare necessary to fracturethe hair which eventuallywill lead to a split end. However there are many factorswhich weakenthe hair that predispose it to split during the combing process(6). There are many references on the effectsof UV on the degradationof the differentstructuresof hair. One referenceis a reviewof our currentunderstandingof the subjectandoptionsfor photoprotection (7). Other damagingfactorsthat arenoteworthy to mention are chemical processingsuch as bleaching (8), thermal (9), thermalmechanicaldamage(brushand blow dry) (10), and damagefrom surfactants which can be translatedto multiple shampooing (11). Evenif hairhasnot beenpurposelydamaged, the hair at the tip end beingolderthan at the root hassufferedmorewearand tearand would tend to split during combing.It is necessary thereforewhen designinga test method that will be usedto test the efficacyof a compositionto mend split endsto incorporate into the procedurethe samecombingforcesthat arepresentduringeveryday grooming.Without this the fibers will not be subjectedto the samedegreeof shear forcesduring combingand the durability of the mendedfiber cannotbe assessed. This aspectof testingthe durabilityof the split endmendhasbeenincorporated into the test method usedin this study. Subjectinghair to realisticcombingforcesallowsthe assessment of not only the initial mendingafter treatment,but more importantlythe durability of the mend suchas a post combing treatment.With this method various Figure 2. Dynamicbendingof hair as combis passedthroughtress. 454 JOURNAL OF COSMETIC SCIENCE polymer systemswere testedfor their ability to mend split ends.The experimentation evolvedfrom testingindividualpolymersto polymerblendswhereit wasdiscovered that a polyelectrolytecomplex,formed betweenthe ionic interactionsof two oppositely chargedpolymers,providedpositiveeffectsin the mendingprocess.The novelcomposition wasfoundto havedurability to a postcombingtreatmentand wasstill able to be washedoff the hair after a post shampootreatment. Basedon these featuresit was characterized as a semi-permanent hair repaireffect.Besidesa descriptionof the polyelectrolytecomplexusedin this study, as well as test results,a proposedtheory of the mechanismof mendingis described.This mechanismservesas a model for designing other complexesthat will have the samehair mending effect. MATERIALS AND METHODS MATERIALS Natural brown hair tressesare suppliedby InternationalHair Importersand are made with their patentedswatchingprocessto be 3.5 gramsof loosehair, 6.5 inchesin length from the bottom of the sewnend to the tip of the hair, and 1 3/4 inchesacross.Brand of combsusedin the experimentsare Sally'sBeauty Supply. Fine teeth sectionof the comb containseight teeth per centimeter. The freeacidform of the copolymerof methyl vinyl etherandmaleicanhydride(INCI: PVM/MA Copolymer)is suppliedby International SpecialtyProductsunder the trade nameGantrez© S-97 BF Polymer.The copolymer of vinyl pyrrolidoneandmethacrylamidopropyltrimethyl ammonium chloride (VP/MAPTAC Copolymer; INCI: Polyquaternium-28)is supplied by International SpecialtyProductsunder the trade nameConditioneze © NT-20. This is a 20% (w/w) solutionin water.Theseingredients are usedas suppliedand not purified or modified in any way. Figure 3 illustratesthe structuresof thesecompounds. A commercialproduct with a split end mending claim was usedas a benchmark.Its' ingredientlabel is: Aqua/Water, Cyclopentasiloxane, PropyleneGlycol, Hydroxypropyl Guar, Phenoxyethanol, Peg 40 HydrogenatedCastorOil, PEG/PPG-17/18 Dimethicone, BehentrimoniumChloride, Aminomethyl Propanol,Trideceth-12, Polyquaterium-4, Dimethiconol,Limonene,Linolool,BenzylSalicylate,Amodimethicone, AlphaIsomethyl Ionene, Perea Gratissima/AvocadoOil, Carbomer, Potato Starch Modified, Methyl Paraben, Butylphenyl Methylpropional, Citronellal, Cetrimonium Chloride, Laureth-23,Laureth-4,PrunusArmeniaca/ApricotKernel Oil, Coumarin,Hexyl Cinnamol,Parrum/Fragrance, F.I.L. C1638713 EQUIPMENT © Nikon SMZ 1500 Stereomicroscope © Linksys2.2 programfor digital imagery(Linksysfor Windows, Linkam Scientific InstrumentsInc., 8 Epsom Downs Metro Center, Waterfield, Tadsworth,Surrey, KT205HT, U.K.) ß Thermal/MechanicalStyling Apparatuscustombuilt at ISP to producetresseswith split ends. © Amray model 1820/D digital ScanningElectron Microscope(SEM) with a LaB6 2006 TRI/PRINCETON CONFERENCE 455 OCH3 I CH --CH2 -- CH CH I I O:C C:O I OH I OH INCI: PVM/MA Copolymer CH• -CH• OH I I CH CH• I C--O I NH CI H•)• I H•C• N+---CH• I CH• INCI' Polyquatemium-28,(VP/MAPTAC Copolymer) Figure 3. Polymersusedto form complex. electronsource,usedto obtainhigh resolutionimagesof fibers.The unit is capable of magnificationup to 100,000x. ß Malvern MastersizerS, usedto measureparticlesizedistributionof microgelsof the complexin water.It determinesparticlesizedistributionof the liquid dispersions by using Mie laserlight scatteringtheory.Mie theory, unlike Fraunhofer,allowsconsiderationof particle refractiveindex, required for reliable results on particles <10 pm. METHODS Production ofsplitendsonhair tresses with a thermal-mechanical apparatus. The hair obtained 456 JOURNAL OF COSMETIC SCIENCE from InternationalHair Importersis essentiallyreceivedundamaged.In order to start the experimentation,hair needsto be damagedto createsplit endsfor repair.This is accomplished with a thermal/mechanical styling apparatus.This apparatusconsists of two vent brushesthat are attachedto a cylindricalmixing blade.This is madeto rotate with a mixer situatedin a horizontalinsteadof its' normalverticalposition.The mixer is adjustedso that it is made to rotate at 75 rpm againsta hair tress.This treatment equatesto approximately9,000 brush strokesan hour. Simultaneously,the hair is subjectedto the hot air of a blow dryerwhichis situatedto keepthe hair againstthe brushesduring rotation. This treatmentsimulateswhat a consumerdoesduring the styling process. This apparatushasbeenpreviouslyusedfor assessing the ameliorating effectsof conditioningagentsagainstthe damageincurredby both thermal and mechanicalstress(10). Prior to attachingthe hair to the apparatus it is first dampenedby rinsingfor 10 seconds with warm tap water and combedthroughwith a plasticcomb to removeanysnags.The hair tressis then put on the thermal/mechanical apparatus.The hair tressis subjectedto this thermal/mechanical stressfor 1.5 hoursat 75 rpm. The hair blowdryeris setat warmandlow fan andis pointedat the middleof the tress.The brush is set to a positionto traverseat least3Aof the tresslength. At the end of the process, the hair tressis examinedunderlow magnificationto confirmthat it is easyto find 20 split endsacrossthe hair tress.If not, then more brushingis doneuntil a satisfactory number of split endsare produced. Pretreatment procedures. A split end fiber is isolatedin the tresswith the useof a magnifyingglassandtweezers.The fiber is labeledat its root end.Split endfibersarechosen uniformlydistributedthroughoutthe tress.A dot is drawnwith a redpermanentmarker slightlybeforethe beginningof the split to later determineif the split brokeoff after combing.This procedureis repeatedfor 20 split endsfor eachtress.A total of five tresses aretaggedin this way for a total of 100 fibers.This is the quantityof split endsfor the study of one formula and providesa statisticalbasisfor the results. Picturesof eachsplit end are taken under the stereomicroscope at 20x. The digital pictures for all of the 100 split end fibers are savedand their files are labeledas pretreatment.Data is tabulatedin a chart as is illustratedin Table I. The following scoringsystemis usedfor futurequantificationof split end repair:end split = 1; no split = 0; partial split = 0.5. The differentdegreesof splitsare illustratedin Figure4. First thereis the majorsplit which is termedprimary.A split end within a split is termedsecondary. Finer splitsat the tertiarylevelarealsoobserved at the 20x magnification.Eachtype of split is scored and tabulatedin eachstep of the process.In this experimentonly primary split end mendingwill be reportedsincethis is observable with the nakedeyeand hasthe most effect on whole hair attributes. Posttreatment andwithouts•bjecting thetress to•vmbing. The tresses arefirst washedwith 3% Ammonium Lauryl Sulfatesolutionfor one minute and then rinsed well. The excess water is removedfrom the tressand 0.50 gramsof the test compositionis addedto each tressand distributeduniformlywith the help of combing.The tressesare then allowed to air dry. When the tresses aredry they aregentlystrokedto breakany adhesionof the fibersfrom the effectsof the treatment.As in the pretreatmentstep,picturesareagain taken under the stereomicroscope for eachof the 100 taggedfibers and their digital picturesarefiled anddesignated asposttreatmentbeforecombing.Split endmending assessment is again tabulatedin the chart in Table I. 2006 TRI/PRINCETON Table CONFERENCE 457 I Tabulation of Data and Calculationof Mending for One Tress After leave-on After leave-on treatment Fiber# Before treatment P treatment (beforecombing) (after combing) S T P S 1 1 0 1 0 0 T 0 1 P 0 S T 0 2 1 0 0 0 0 0 0 0 0 3 4 1 1 0 1 0 0 0 0 0 0 0 0 0.5 0 0 0 0 0 5 6 1 I 2 1 0 0 0.5 0 0 0 0 1 0.5 0.5 0 0 0 7 1 1 0 0 0 0 0 0 0 8 1 0 0 0 0 0 0 0 0 9 1 0 0 0.5 0 0 0.5 0 0 0 10 1 0 0 0 0 0 0 0 0 11 1 0 0 0 0 0 0 0 0 12 1 1 0 0 0 0 0 0 0 13 14 1 1 1 1 0 1 0 0 0 0 0 0 1 0 0 0 0 0 15 1 0 0 0.5 0 0 1 0 0 16 1 0 0 0 0 0 0 0 0 17 1 0 0 0 0 0 0 0 0 18 1 0 0 0 0 0 1 0 0 19 1 0 0 0 0 0 1 0 0 20 1 0 0 0 0 0 1 0 20 7 3 1 90 95 0.5 85.7 92.8 8.5 50 57.5 0.5 85.7 92.8 Total split end Complete mending (%) Total mending (%) 0 100 100 Durability Index D 0.61 0 0 100 100 1 1 History of mendingfor eachfiber asobservedwith stereomicroscope (1 = end split; 0 = intact end; 0.5 = partial split; P = primary split; S = secondarysplit; T = tertiary split). Durabilitystep--Posttreatment with combing thehair tress. Eachhair tressis combedtwenty times with the fine teeth of the comb. Picturesof the taggedfiber endsare again taken under the stereomicroscope and their files labeledas post treatment with combing. During the observation of eachfiber the permanentmark is identifiedasa landmarkto make surethe end of the split fiber hasnot brokenoff to guardagainsta falsepositive mending effect being recorded.Scoringis tabulatedas beforeas is seenin Table I. CalcMationof split endmending percentage. The following two equationsare usedto calculatethe degreeof split end mending. Total mending% = Total # splitendsbeforetreatment- # splitendsaftertreatment Total # splitendsbeforetreatment x 100 Total percentmendingincludesthe assessment of both completeand partial splits. Scoring:1 = split end, 0 = mendedsplit, 0.5 = partially mendedsplit. Total mending% after combing Durability Index (D)=Total mending %before combing Therefore, the maximum D -- 1.0, and the minimum D -- 0. 458 JOURNAL OF COSMETIC SCIENCE :Fiber 2 before treatment SecondarySplit PrimarySplit •' •90 urr• Figure 4. Stereomicroscopic view of fiber (20x) showingprimaryand secondary levelsplits. All of the resultsreportedin this study are basedon total mendingwhich includesthe assessment of both completeand partial mendingof the split end fiber. An exampleof the calculationof the tabulateddata for oneof the five tresses of a study is foundat the bottom of Table I. Again, althoughthe secondaryand tertiary level splitsare assessed as well moreemphasisis placedon the primary splitssincetheseareapparentto the naked eyeand their mendingwould afforda consumerperceivablebenefit. Illustrationof complete andpartial mending. Figure 5 showsthe three stagesof the measurementcyclenamelypretreatment,post treatmentbeforecombing,and finally post treatmentafter combing.The last step teststhe durability of the mend. The red dot madewith the permanentmarkercanbe observedjust prior to the split end. This series of photosin Figure 5A) servesto exemplifycompletemendingof the split end. Figure 5B) showsan examplewherethe fiber hasbeenpartially mendedafter treatmentand stayspartially mendedafter the post combingprocess.In this casea scoreof 0.5 would be assigned.Both completeand partial mending are taken into considerationin the assessment of mendingand is designatedas total mending. Advantages of the testmethod. Sincethe tagged split end fibers are part of the trees, applicationof the treatmentcanbe performedin a realisticfashionsimulatingconsumer usage.In this experimentthe product is applied to damp hair and allowed to air dry. However,the methodallowsthe studyof differentapplicationtechniquessuchasbrush and blow drying or addingthe treatmentto dry hair for example. The advantageof the taggingprocessallowsthe studyof the fate of the split end after 2006 TRI/PRINCETON ^) CONFERENCE 459 B) Pretreatnlent Post treatment beforecombing Post treatment ..... after combing • Figure 5. Examplesof the two typesof mendingthroughthe threestagesof measurement: (A) Complete mending:split end is completelymendedfrom startof fissureto endof fiber. (B) Partialmending:split end is mendedfrom start of fissureto a fractionof the length to the end of the fiber. treatmentand moreimportantlyto durability to combing.Sincethe fiber is still part of the tressit canbe subjectedto normalcombingforcesor othertreatmentsto determine the effectiveness of the split end mendingproduct.In this casethe tressis subjectedto twenty combingsafter applicationof the formulation.Combing was chosento test durabilitysince,asdescribed above,the majorcauseof split endformationis throughthe shearstresses generatedduring the combingprocess. Also,the taggingprocess allowsthe study of other treatment variablessuchas survivabilityafter washing,the effect of multiple treatments,or someother regimendesignedby the experimenterto test split end mendingdurability. Another advantageto the method is the increasein the depth of field that the stereomicroscope possesses overthe opticalmicroscope. As canbe seenin Figure4, the whole fiber end canbe focusedand observedunderlow magnification.In the figure it canbe observedthat this split end hasa major bifurcationwhich is termedprimary, and two minor splitswhich are termed secondary. The stereomicroscope alsoallowsthe observationof the fiber unhampered by a coverslip whichmaydepress the fiber to the point wherethe split end will close.A slight shadowcanbe observedfrom the light source abovethe specimenshowingthat the fiber is not laying flat on the stage. PRODUCTION OF POLYELECTROLYTE COMPLEX Table II comprises the formulationusedin the test. Test formulasutilize the complex 460 JOURNAL OF COSMETIC SCIENCE Table II Formationof Complexand Formulationof Split End Mending Serum(6lB) Ingredients Phase A Deionized water 49.00 Xanthan gum (RhodicareT) Phase 0.50 B Deionized water Polyquaternium-28 (conditioneze© NT-20) Phase %w/w 36.00 9.00 (1.80 active) C Deionized water 4.24 Sodiumhydroxide(10% Aq. Soln.) PYM/MA copolymer(Gantrez© S-97 BF Polymer) Propyleneglycol(and)diazolidinylurea(and) iodopropynylbutylcarbamate (Liquid Germall© Plus) 0.56 0.20 0.50 100.00% Percentactive complex= 2.00%. Ratio of PVM/MA copolymertO Polyquaternium-28= 0.20:1.80. at 2 percentactivewith a ratio of PVM/MA Copolymerto Polyquaternim-28of 0.20 to 1.80 respectively. The procedurefor putting the full formula together(6lB) which includesthe productionof the complexis as follows. Procedure for full formula 1. In main containerdisperseXanthan Gum into room temperaturewater with moderatepropelleragitation.When fully incorporatedswitch to moderatesweepagitation and mix until uniform. 2. Add water of phaseB in a premix containerand mix with moderatepropeller agitation.Add Polyquaternium-28(ConditionezeNT-20) and mix until uniform. 3. Add waterof phaseC to a separatepremix containerandmix with moderatepropeller agitation.Add sodiumhydroxidesolutionandmix until uniform.SprinklePVM/MA Copolymer(GantrezS-97 BF Polymer)into vortexandmix until uniform.AdjustpH to 6.95 + 0.05 with sodium hydroxidesolution. 4. Increaseagitationof contentsof phaseB (-1000 rpm). Add phaseC to phaseB over the courseof 20-30 seconds. Mix with fastpropelleragitationfor ten minutes. 5. Add combinedphasesB and C to phaseA. Mix until uniform. 6. Dissolvepreservative and mix until uniform. 7. Adjust pH to 7.1 + 0.1 with 10% citric acid solution. It is importantto add the anionicpolymerto the cationicpolymerwhen formingthe complex.Also,the complexshouldbemadeprior to its incorporation into a formulation; the stepsin the aboveprocedurefor making the complexare 2 through 4. When incorporatingthe complexinto a formula the integrity of the complexis judged microscopically to determineif it hasa typicalmicrogelstructurewhichis described below. This is a predictiveindicatorfor the efficacyof the complexto repairsplit ends.The complexhas shownto be compatiblewith nonionicand mildly cationicand anionic polymers.In this casethe complexis addedto the anionicpolymerXanthanGum to makea serumproduct.One of the controlformulasis madeby addingthe complexalone to water to obtain two percentactive. 2006 TRI/PRINCETON RESULTS AND FORMATION AND CONFERENCE 461 DISCUSSION CHARACTERIZATION OF POLYELECTROLYTE MICROGEL COMPLEX There have been variousnamesfor polyelectrolytecomplexes.These consistof such namesas polymer-polymercomplexes,or interpolyelectrolytecomplexes.Despite their nomenclatureas used in the academicliterature they are describedas two speciesof polymersthat caninteractwith eachother without the formationof covalentbonds.The bondsinvolvedcouldbe electrostatic, hydrogenbonding,Van der Waals interactions,or a combinationof each.The polyelectrolytecomplexusedin this study is basedon the electrostaticinteractionsof two oppositelychargedmolecules.It is not just a mixture of two polymers.As canbe seenin Figure6 high molecularweight linearpolyanionicand polycationicpolymerswhen combinedtogetherform a complexthrough the association of their oppositecharges(12). There are numerousfactorsthat shouldbe briefly mentioned at this point that are important in the formationof the complex.Besidesconsideringthe weight ratiosof the two unlike chargedpolymersother factorsinvolvedin the interactionaremolecularweights,chargedensities,pH and electrolytecontentof the solvent,the solventtype, and the process' of putting the two polymerstogether.Since unlike chargesinteract on a molar basis,the stoichiometryand chargeratios are important in consideringtheir interaction. The hypothesiswas that split end mending can be achievedwith a polyelectrolyte complexmade through the interactionof two oppositelychargedpolymers.This is in distinction to split end mending with a polymer-surfactantcomplexas patented by Ramashandranet al. (13). They invented an ingenioushair rinse compositionthat claimedwouldnot only conditionhair to providesuchpropertiesaswet detangling,but also lend fixative propertiesand repair split ends. The three main ingredientsthat comprisedthe rinse are quaternaryammonium salts(quat), water insolubleacrylic or acrylate polymers and a solvent that comprisesa long chain alcohol and/or alcohol ethoxylate.The solventis usedto help compatibilizethe quat and polymer. It was theorizedthat the quat and polymerform a complexwith eachother in the solventand Polyanion Polycation Polyelectrolyte Complex Figure 6. Ionic association of polyelectrolytes of differentchargethat formsa complex;adaptedfrom reference(12). 462 JOURNAL OF COSMETIC SCIENCE aids the depositionof the anionicpolymer on the hair during the rinse cycle which would otherwisebe washedaway.They alsotheorizethat split end mendingis achieved by the adhesiveness of the depositedpolymerwhich when dried formsa film that holds the splits together. Using the specializedtest methodasdescribedin the methodssectionaboveallowedthe screeningof many typesof compositions which led to the formationof the hypothesis. Someindividualpolymersor mixturesof polymersgaveonly a poor to fair mending durability efficacy.The compositiondiscovered basedon a polyelectrolyte complexwas found to haveincreased/mending durability efficacyover controlsystems.The anionic polymer of this complexis PVM/MA Copolymer.The anionic contributionof this moleculedependson pH since it has two carboxylicgroupsper monomer unit. The cationic polymer component is Polyquaternium-28 or VP/MAPTAC Copolymer. Its cationicityis from the quaternarygroupsand are positivelychargeddespitepH. The electrostaticinteractionthen is betweenthe ionizedcarboxylicgroup of the anionic polymerand the quaternarynitrogengroup of the cationicpolymer(14). When the complexformsit canbe characterized microscopically asa microgelstructure. Figure7 showsthe characteristics of thesemicrogelsbasedon the polyelectrolyte complex as observedunder an optical microscopeat 500x. It can be observedthat these particlesare translucent,non-uniform in shape,and are dispersiblein the aqueous ..50.x!ens ß •30um• Mi ge! . : 2.00% active complex cmprising 0.2ø&PVA Cpolymer 1.8- Polyquatemmm-28 Figure 7. Microgel structureas observedunder optical microscope(500x) 2006 TRI/PRINCETON CONFERENCE 463 solvent.Stability showsthat a 4% activecomplexdispersionis stableat elevatedtemperaturesandmultiple freezethawcycles.The particlesarein the rangeof 5-10 microns in sizeasmeasuredwith a Malvern particlesizeanalyzer.The particlesizedistribution is illustrated in Figure 8. By studyingthe phasediagramformedbetweenPVM/MA Copolymerand Polyquaternium-28 the phaseregionsof their interactionswereidentified.In building this phase diagram variousweight ratios were usedin putting the two polymerstogether while keepingothervariablesconstant.The variableskept constantwerethe solventwhichwas water, pH of the PVM/MA Copolymerwhich wasadjustedto 7.00 + 0.05, and the type of polymerwhichinherentlycontrolsthe molecularweight andotherintrinsicproperties of the polymerssuchascationicchargedensity.The process of putting the two polymers togetherwasalsokept constant.The characterof the polymercombinationswere noted and given a value againstset criteria.The phasediagramwasproducedby regression analysiswith the help of statisticalsoftware(15). The resultantphasediagramis illustrated in Figure 9. The complexeswere characterizedmacroscopically by appearance wherethe value of 5 wasgiven to clearsolutions,1 wasgiven to opaquewhite dispersions,and 2 through4 for intermediatevaluesfor solutioncharacters; seelegendin Figure9. It wasfirst thoughtthat the opaquemilky white dispersions designated1 only . , , i , . ii] . 0_1 , ! i i .ll ! lJl . ] i . i i[ i i,i 11111 i [i ! . , i , .! i i 1110_0 Figure 8. Malvernparticlesizeanalysisof microgelstructure. . ! 464 JOURNAL OF COSMETIC SCIENCE DESIGN-EXPERT Plot 0.50 Phase Behavior O Des•jn Points Phase Run Behavior = 1.564 0.38 X: A: Polyquaternium-28= 1 .80 Y: B: PVM/MA Copolymer = 0.20 '• 0.25 Solution Character ComplexTested o o Legend: I = Milky • 0A3 2 = Very hazy 3 = Hazy 4 = Slightly hazy 5 = Clear 0.00 2.44 4.88 7.31 9.75 A: Polyquaternium-28 Figure 9. Phasebehaviorof polymersof differingcharge. containedthe complex,but with further investigationunder the microscopeit was observedthat all dispersionsother than the clear onescontainedmicrogels.It was concluded that the white opaquedispersions thenhadthe highestintensityof microgels formedand would be mostappropriatefor testingthe split end mendingbenefit.The complextestedin this studyis identifiedin Figure9 and consists of two percentactive complexmadeby combiningPVM/MA CopolymerandPolyquaternium-28 at a weight ratio of 0.2 to 1.8 respectively. Polyelectrolyte complexes basedon otheranionicand cationicpolymercombinations werestudiedin thiswaybut havenot beentestedformendingefficacy. Complexes using PVM/MA Copolymerasthe anioniccomponent havebeenformedwith Polyquaternium7, 10, and 11. Also,Vinylpyrrolidone/acrylates/laurylmethacrylate copolymerservingas the anionicpolymerhasbeencomplexedwith Polyquaternium-28. The phasediagrambuilt in Figure9 is basedon weight ratiosof the two polymers. However,the two polymersareactuallyinteractingon a stoichiometric basisthrough their chargeinteraction.To furtherelucidatethe interactionof thesetwo polymersthe followingstudywasconducted andis illustratedin Figure10. Variouslevelson a weight basisof Polyquaternium-28were combinedwith 0.2% PVM/MA Copolymer.The resultantviscositywas measuredusing a Brookfieldviscometerwith a small sample adapterandthe viscosityplottedagainstthe calculated moleratioof cationicmonomer to anionicmonomer.The shapeof the curveis distinctlyparabolically curvedcontaining a minimum viscosity.It was discovered that this minimum of viscosityoccursat a 2006 TRI/PRINCETON CONFERENCE 465 lOOO Excess polyanions; Excess polycations lOO ß PVM/MA0.2% lO ..l•. iEnd point::C*/•'2 =1 1 o.oo 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 UnitmoleratioofPolyquaternium-28 to PVMIMA Copolymer Figure 10. Dependenceof viscosityon unit mole ratio cationicto anionicgroups. stoichiometricchargeratio of oneto onewherethe stoichiometricequivalence of cationic and anionicchargesarethe same.This indicateda maximumin the amountof microgels formedsincetheseare discreteparticlesthat are dispersedin solution.Polymer ratios deviatingawayfrom the oneto onestoichiometricequivalence would containpolymer not associated in a microgeland would increasethe viscosityof the solution.The lower viscosityevidentfor the 1:1 ratio wasdue to the hydrodynamicvolumeof the complexed chainsbeing smallerthan when free un-complexed polymersare presentin solutionat otherchargeratios.This charge-charge interactioncontributesto the compactnatureof the microgelstructureof the complexand exemplifiedthe stoichiometricinteractionof the two polymers.It wasdeterminedthat the complexchosento repair split endshasa cationicto anionicchargeratio of precisely1.14. MENDING TEST RESULTS OF MICROGEL COMPOSITION A screeningstudy showedthe efficacyof the polyelectrolytecomplexin split end mendingdurability. The controlsystemswerebasedon the componentpolymersof the complexusedalone and a clear 1:1 mixture of the two polymerswhere there are no discretemicrogelspresent.All polymer and polymer combinationswere kept constant at a total of 2.00% active.This screeningstudyconsistedof measuringtwenty tagged fibersfor eachformulationinsteadof the usualonehundredand wasbasedon complete mendingasobservedwith a magnifyingglass.Test resultsshowedthat the complexhad increased durability of mendingoverthe controlformulations.Test resultsare in Table III. When the complexwas usedalone at 2.00% active in a one hundredfiber study it mended92 out of 100 fibersafter treatmentand beforecombing.After combingthe tresstwenty times 68 fibersremainedmended.When the 2.00% activecomplexwas formulatedinto a simple lotion formula thickenedwith Xanthan Gum approximately 466 JOURNAL OF COSMETIC SCIENCE Table III ScreeningExperimentShowingEfficacyof ComplexOver SystemsUsed asControls % Mending after % Mending after Durability Formula type treatment combing index 2.00% neutralizedPVM/MA copolymer 2.00 % Polyquaternium-28 2% Complex;0.20 neutralizedPVM/MA copolymerand 1.80 polyquaternium-28 1.00% neutralized PVM/MA copolymerplus 1.00% polyquaternium28 90 75 15 0.17 4O O.53 90 75 O.83 85 2O 0.24 the sameresultswere obtained.This providedevidencefor two things.First, that the resultswere reproduciblegiving validity to the test method. Second,the complexcould be formulatedinto a systemwithout lossof efficacy.Resultsareportrayedin Figure 11. In both casesthe durability indicesof the mending after combingwas over 70%. As mentionedin the procedurethere are 100 fiberstestedfor eachtreatment,twenty fiberstaggedon one tresstimes five tresses.The data illustratedin Figure 12 showsthe variability of mending for each tressfor both beforeand after combingon the full formulation.The averageand standarddeviationof the mending resultsafter combing of the five tresses is 67.6 + 12.6%. Comparingthis mendingdatato a controlformula containingjust the thickeningagentascanbe seenin Figure 13 showsthe significance of the difference.From this it can be concludedthat the complexis responsible for the high mending scores. Stereomicroscopy Results of Mending Efficacy Primary Splits, Complete+partial Mending 100 92 93.3 80 ß Complex alone, 149A Inafull formula, 61B 1 ....... 68 6716 ................ / 40 20 0 I before combing after combing Figure 11. Total percentmendingof complexaloneand in a frameworkformulaboth beforeand after combing. 2006 TRI/PRINCETON CONFERENCE 467 Stereomicroscopy Results of Mending Efficacy Primary Splits, complete+partial mending lOO 95 92.5 95 Ave. 9o = 93.3% +/- 2.4% 8o 7o average of 100 fibers, 6o 67.6%+/-12.6% 5o mending after combing 4o 3o 2o lO o tress 1 tress 2 tress 3 tress 4  before combing El after tress 5 combing 1 Figure 12. Varianceof mending efficacyfor five tressesusedin one experiment. Complexesbasedon differentweight ratiosof cationicto anionicpolymerweretestedfor split endmendingefficacy.It wasdiscovered that althoughthereweremicrogelsformed by the interactionof Polyquaternium-28and PVM/MA Copolymer,an optimalamount of repair was evidentwhen the two polymerswere combinedwhen their chargeratios were 1:1 as can be seenin Figure 14. Split end mendingefficacyis reducedas the polymerratio deviatesfrom the one to one chargeratio. This is further evidencein showingthe importanceof the polyelectrolytecomplexin mendingsplit ends. The advantage of thedeveloped methodis to determinethe fateof the splitendsthrough varioustreatmentsthat test the durabilityof the mend.Sincethe taggedsplit endfiber is alwayspart of a tressit can be treatedin sucha way that it is exposedto realistic treatments.In the previouscasethe tresswas subjectedto a controlledamount of combingto testthe durabilityof the mend.Other treatmentregimenscanbe conceived to test durability in a realisticfashion.A test was devisedto determinethe effectof multiple treatmentsof the formulawith the complexand its removabilitywith shampoo. One cycleconsistedof treatmentwith the formula, drying, combing,and then washing.Split end mendingwas assessed after treatmentbeforecombing,after treatment after combing,and finally after washingfor one, two and five cyclesof the treatment schedule.Resultsof the test are illustrated in Figure 15. First it can be observed that mendingis high after treatmentbut beforecombingfor treatmentcycle onethroughfive. Durability to combingstressoverthe multiple treatmentcyclesstays the sameand is approximately60%. Durability to washingis low and decreases with continueduse.It wasobserved duringthe mendingtabulationthat the split endsbecame moreseverewith continuedwashingwhichexplainsthe loweringof the percentmend- 468 JOURNAL OF COSMETIC SCIENCE Stereomicroscopy Results of Mending Efficacy primary Splits, complete+partial mending lOO 93.3 90 80 70 • 67.6 before comb  aftercombing 60 50.4 50 40 30 ' ,,, 20 lO ,,, o with complex(11110-61B) No complex(11203-152A) Figure 13. Total percentmending of formulawith complexvs control. ing scoresafter multiple washcycles.Measurements taken beforeand after treatment after one cycle are approximatelythe sameas the previousdata and show again the reproducibilityof the data. The implicationsof theseconclusions related to consumer performanceincludethat the productcan be claimedthat it will not havethe negative effectsof build up with continueduseand that productdirectionsshouldincludeadding the productto the hair after everyshampooin order to obtain the desiredeffect. There are few commerciallyavailableproductson the market that claim split end mending.The onefoundwastestedasa benchmark for performance to the formulawith the polyelectrolyte complex.Althoughthe commercialproductwasable to mendsplit endsinitially aftertreatment,the mendsfailedafterpostcombing.Total percentmending is considerably loweraftercombingfor the commercialproductvs. the formulawith the polyelectrolyte complex(Figure 16A). Durability index of the commercialproduct is muchlowerespecially forprimarysplit ends(Figure16B).The mechanism responsible for temporarilymendingsplit endsin the commercialproductis probablythrougha loweringof the surfaceenergyof the fibersafter treatment.The damagedpartsof the fibersare then attractedthroughweakhydrophobic bonds.Ingredientsresponsible for this are the blend of siliconesin the productsuchas cyclopentasiloxane, dimethicone, alkyl modified dimethicone,dimethiconol,and amodimethicone.Other ingredients having the sameeffectare the cationicsurfactantsand organicoils; refer to methods sectionfor ingredient labeling. This hydrophobicmechanism,although it providesa high degreeof mending,fails to providedurability to the mend as exemplifiedin the 2006 TRI/PRINCETON lOO CONFERENCE 469 Mending Efficacy vs. Charge Ratio of Polyquaternium-28 to PVMIMA Copolymer 90 0.90 0.80 80 0.70 ... 70 0.60 60 t. 50 0.50 • 0.40 .•. "- 40 0.30 30 0.20 20 0.10 lO ........:.................... •................................ . o 0.6 0.4 •, •, .... 0.8 1 ..................... '•.................?........................ 4 0.00 1.2 1.4 1.6 1.8 2 Charge Ratio mending% before combing m mending% after combing durability ---- ---- Poly. (durability) Poly.(mending% after combing) Poly.(mending% before combing) Figure 14. Mendingefficacyvs chargeratio of cationicto anionJcpolymer. B) Durability Index A) Total % Mending of Primary Splits lOO 60 .,0.60 .... 40 0 , CycleI , Cycle2 Cycle5 G Total % Mending Before Combing i• Total % MendingAfter Combing I• Wash 0.40 0.20 ..... 0.00. , CycleI Cycle2 Cycle5 I•Durability Index Combing Durability Index Wash Figure 15. Ctmqulative effectsandmendingdurabilityto washingoverthe courseof five cycles.(A) Total percentmendingof primarysplits.(B) Durability index. postcombingdurabilitytest.The hydrophobic bondingof the components of the split fiber is not strongenoughto withstandthe stressof the combingprocess. In our screeningexperimentsfor the polyelectrolyte complexit wasfound that there weremanycompoundsthat couldmend split endsprior to stressingthe tressto test the durabilityof the mend.It wasthe ability of the complexto durablymendthe split ends after this post combingprocessthat providesthis semi-permanent mendingability. Basedon the surfacecharacteristics of damagedhair aswell asthe structureand chemical interactionsof the polyelectrolytecomplexwith hair, a theory was proposedon the possiblemechanismof this semi-permanent split end mending. PROPOSED THEORY OF SPLIT END MENDING Hydrophilic character of damaged hair. Human hair consistsof a centralcorecalledthe 470 JOURNAL OF COSMETIC SCIENCE A) Total % Mending of Primary Splita B) Durability Index 100 1 90 80 70 60 30 2o 02 lo 01 o Commercial Product Split End Mending Serum 61B Commercial Product SplitEndMendingSerum61B [Before Combing After Combing] Figure 16. Comparison of mendingwith complex vsa commercial product.(A) Totalpercentmendingof primary splits. (B) Durability index. cortexcoveredby a sheathof severallayersof flattenedcuticle cells. Each of these overlappingscalesis abouthalf micronthick and45 micronslong.The thin outermost layer that formsa sheatharoundthe cuticlecell is known as the epicuticleand is hydrophobic, whereas, the cortexis hydrophilic(16). The outerlayerof cuticlesurface contains18-methyleicosanoic acid (18-MEA) alsocalledthe F-layer,which makesthe hair surface hydrophobic. 18-MEA bindswith theA-layercontaining cystinegroupsin the cuticlecell.The mainfunctionof the cuticleis to providemechanical protectionfor substances insidethe cortexlayersuchas preventingaminoacid and proteinsfrom washingout throughthe hair surfaceor protectingit from furtherdamage.When hair becomes damagedtherearebothphysicalandchemicalchanges to boththe surface and internalstructures of the hair fiber.The morphological changes of a damagedhairfiber areevidentasillustratedin Figure17. Besides theobvioussplitin thefiberexposing the subassemblies of the cortexit canbe observed that the cuticleis partiallylifted aswell. Fora damaged hairfibercontaininga splitend,asshownin the SEMpicture,thecuticle layersarechemicallydamagedaswell resultingin the hair fiberbeingmorehydrophilic. Thismightbedueto theexposure of thecortexaftercuticledamageand/ortheexposure of theA-layerin cuticlecells.The A-layercontains highlevelof cystinegroups(>.30%). The disulfidebondin cystine,-R-S-S-R-, is veryreactiveandis in a stateto be oxidized. One of the possible oxidationproducts of cystineis cysteicacid,R-SOj. Whenthe F layer is strippedthe increased levelsof cysteicacid on the damagedhair surfacewill contributeto its increased hydrophilicity. A simpletestdemonstrates that damaged hairismorehydrophilicthanundamaged hair. A hair tip with a split end anda healthyhair tip weresoakedin a 0.03% cationicdye solutioncalledSafraninusedin microbiologicalstainingfor 30 seconds and rinsedin runningwater.The hair fiberswerethen observed undera stereomicroscope. The microscope imagein Figure 18 showsthat the split tip end turnsto a muchmorered color than the healthyhair. This is dueto the higherinteractionof the cationicstainwith the increased numberof anionicsitesof the damagedfiberwhicharedueto the chemicaland morphological changes in the hair surface.The positiveresponse to stainingindicates that the hair surfaceor cuticlecellsare damagedafter the hair fiber splits and is consistentwith the SEM resultsin Figure 17 which showsthe cuticledamagecharacterizedby jaggededges. Besidesthe stainingtest therehavebeenmany studiesthat showthat the hair surface becomes morehydrophilicor morenegativelychargedwhendamaged. For example,it hasbeenreportedthat the hair surface becomes hydrophilicbecause of the exposure of uncovered A-layerafter exfoliationof hydrophobic F-layerby the actionof hydrogen 2006 TRI/PRINCETON I CONFERENCE 471 . .. Figure 17. SEM showingsplit end and cuticle lifting. peroxideand alkali usedin hair coloring(17). Ruetschfoundthat when hair is subjected to chemicaloxidationthat a positiveresponse is obtainedby treatmentwith the cationic fluorochrom,RhodamineB (18). Also, the dye response wasfoundto be directlyproportionalto the treatmenttime. Cysteicacid wasrevealedto be the new specieson the surfaceof the hair basedon chemicalanalysisthroughX-Ray photoelectron spectroscopy. FTIR hasbeenshownto haveutility in measuringthe hydrophilicnatureof damaged hair (8). The disulfidebondwhenoxidizedby a damagingprocess canbedetectedby the shifting bandsin the IR spectrumas the chemicalfunctionalgroupschangeto more hydrophilicspecies. The oxidationproductsformedin hair dependon the natureof the oxidizing agent. Joy et al. reportedthat when hair is treated with alkaline hydrogen peroxide solutions theIR peakat approximately 1040cm -• corresponding to cyteicacid is significantlychangedconfirmingdisulfide oxidation(19). It was also found in the studyby Joy that cysteicacid contentincreases from root to tip end of both naturally weatheredand bleachedhair showingthe increaseof damageof the hair with age. Another piece of evidenceshowingthe increasein the hydrophiliccharacterof the surfaceof damagedhair is an increase in surfaceenergy.Throughthe useof the Wihelmy balancetechniquetestedon singlefibers,it wasfound that both oxidationand reduction increased the wettabilityof the hair (20, 21). They attribute theseincreases to againthe generationof hydrophilicgroupssuchassulfonicacidgroupsin the caseof oxidationand thiol groupsin the caseof reduction. 472 JOURNAL OF COSMETIC SCIENCE Healthyhairtipend -. .. ............ a ,.•::.:....•': •5.•':'•......... Figure 18. Ionic dye reactionto damagedhair. Structure-property relationships are importantfactorsto considerin the process of either choosingor designingingredientsto test for hair repair.One hasto theorizehow the ingredientwill interactwith the fine structureand chemistryof hair in orderto determine if it is a candidatefor experimentation.A few experimentshavebeenshownin this paperthat providesevidencethat therearechangesin the morphologyandchemistryof hair during the damageprocess. One thing that is essentialthereforein the repairprocess is that the ingredienthas to havea cationicnature in order to bind to the anionichair surfaceof the split fibers.Also, adhesiveeffectsare necessary that are able to glue the split subassemblies of the fiberstogether.Lastlyand mostimportantlythe composition needsto be ableto closethe split endsand smooththe lifted cuticlescalessoasto ensure a durablemend especiallyafter combingor other stressfactorsduring for examplehair styling. Consideringthe chemistryand morphologyof the microgelstructureand its interactionwith the chemistryand morphologyof damagedhair, it seemsreasonable that the polyelectrolyte complexis able to meet all of thesecriteriafor the hair repair process.Basedon this thinking a mechanismof actionfor the semi-permanent split end mending effect is proposed. Proposed mechanism of splitendmending with PEC microgel. It hasbeenshownthat maximum mending was achievedfrom microgelsthat were formed from polyelectrolyte complexesmadefrom combinationsof oppositelychargedpolymerscloseto a oneto one stoichiometriccharge ratio. This charge ratio was shown through viscositymeasurementsto be the point of maximumcomplexation.It is believedthat althoughthischarge ratio is balancedthere existsin the microgelresidualanionicand cationicchargesthat 2006 TRI/PRINCETON CONFERENCE 473 havenot associated together.This is because of the sterichindrancethat preventsthe two macromolecules to completelyassociate all of their unlike chargestogetherfor complete neutralization. Therearevariousaspectsto the proposedmechanismof actionof the hair repairprocess with the polyelectrolytecomplex.First, the residualcationicchargeson the microgel would tend to bind to the anionic sites of the damagedcortex through electrostatic association. To showthe cationicityof the complexthe anionicdye, Direct Red 80, was usedas an indicator.Figure 19 showsa split end beforetreatmentwith the complex, after treatment showingmending, and after treatment with Red 80 showinga positive response to the dye. The higherlevelof red towardsthe tip indicatesthe predominance of complex.The red mark just prior to the split end again is the mark made with a permanentmarker. During the drying stagethe microgelcomplexis able to form a crosslinkingstructure which bridgesthe subassemblies of the fiber together.The microgelstructureand its interactionwith hair are illustrated in Figure 20A. The crosslinkingadhesivestructure of the microgelservesto glue the damagedpartsof the fiber together.Sincethe complex is in the form of microgelsin the size rangeof 5-10 micronsthey are small enoughto infiltrate the fissuresof the split cortexespeciallythoseas canbe seenmacroscopically asa split end. The smallerparticlescan to a certainextentpermeatethe lifted cuticle whichis alsopresentin damagedhair. After drying the microgelsform a cleardurable film which tendsto bind thesedamagedpartsof the hair togetheras is illustratedin A) Beforetreatment B) After treatment C) After treatmentplusRed 80 Figure 19. Anionic Direct Red 80 dye test indicatesmore microgeldepositionon tip end. 474 JOURNAL OF COSMETIC SCIENCE Mendin• serum Microgel absorption Lifted cuticle B) drying Mended hair fiber Split cortex Figure 20. Proposed mechanism of splitendmending.(A) Microgelcrosslinking structure. (B) Bindingof cuticle and split end during the drying process. Figure 20B. The uniquefeaturesof the dried thin film ensurea durablemend that will survivethe combingprocess. Thesevariousaspects of the mendingmechanism provides for an efficacious level of mendingthat can endurea postcombingprocess which is typical of normal styling behavior.Visual effectsof this mendingcan be observed throughSEM. In Figure21 it canbe observed that the mendedfiber hasa smoothcuticle where before treatment it was characterizedas lifted. Also, the seam of the weld is evident where the split end usedto be. Having an increased understanding of the formationand chemistryof polyelectrolyte complexes and their interactionwith the chemistryand morphologyof hair allowsthe designof newcompositions that couldfunctionin the samewayasthe complexstudied here. CONCLUSIONS Hair stylingtrendshavecreateda needfor hair repaircompositions that will attemptto restoredamagedhair to its normalstate.Split endsareonemanifestation of that damage. A testmethodhasbeendevisedthat canassess in a realisticfashionthe mendingof split endsthroughvarioustreatmentregimens.The methodis realisticin that the tagged split endfibersarepart of a tressthat canbe subjected to normalcombingor washing cycles.With this methodit has beendiscovered that a polyelectrolyte complexcan semi-permanently mend split endsin that split end hair treatedwith this composition cansurvivethe stressof combing.The composition is efficacious especially in comparisonto a commercialbenchmarkwith a split endmendingclaim.A proposed mechanism of actionhasbeenput forthandconsists of the microgelstructureof thepolyelectrolyte complexactingasa crosslinking structurein the damagedsubassemblies of the damaged fiber.The understanding of this mechanism opensthe wayfor the development of new 2006 TRI/PRINCETON -•' ':.lendi;ng ,ei.a'm:treated. CONFERENCE 475 Mended split Smoothed cuticle Figure 21. SEM imageof hair fiber after mending,showingmendedsplit and smoothedcuticle. combinationsof polymersthat form microgelstructuresafter complexationthat could alsohavea positivebenefitin the areaof hair repair. ACKNOWLEDGEMENTS The authorswould like to thank Bill Thompsonof ISP for SEM andparticlesizeanalysis andAlison Robinsonalsoof ISP for help with opticalmicroscopy and imaging software. REFERENCES (1) A. C. BrownandJ. A. Swift, Hair breakage:The scanningelectronmicroscope asa diagnostictool,J. Soc.Cosmet. Chem.26, 289-297 (1975). (2) J. A. Swift, The mechanics of fractureof humanhair, Int. J. Cosmet. Sci.,21, 227-239 (1999). (3) J. A. Swift,Mechanism of split-endformationin humanheadhair,J. Soc.Cosmet. Chem., 48, 123-126 (1997). (4) J. A. Swift,"Fundamentals of HumanHair Science," Cosmetic Science Monograph Number One,p. 62, Fig. 36. (5) J.A. Swift et al., Flexabrasion: A methodfor evaluatinghair strength,Cosmet. Toiletr.,116 (12), 53-6O. (6) V. 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Ramachandran et al., W096/32920, assigned to Colgate,Oct. 24, 1996. (14) E. Tsuchidaet al., Die Makromolekulare Chemie,175, 583-591 (1974). (15) DesignExpert 6, Star-Ease,Inc., 2021 EastHennepinAve., MinneapolisMN 55413 (2003). (16) C. R. Robbins, Chemical andPhysical Behavior ofHuman Hair, 3•ded.,(Springer-Verlag, NewYork, 1994). (17) S. E. Kelly andV. N. E. Robinson,The effectof groomingof the hair cuticle,J.Soc.Cosmet. Chem.33, 203-215 (1982). (18) S. B. RuetschandY. K. Kamath,Changein surfacechemistryof the cuticleof humanhair by chemical and photochemical oxidation,IFSCC Mag., 7(4), 209-307 (2004). (19) M. Joy and D. M. Lewis,The useof FTIR spectroscopy in the studyof the surfacechemistryof hair fibres,Int. J. Cosmet. Sci., 13, 249-261 (1991). (20) Y. K. Kamath, C.J. Dansizer,and H.D. Weigmann, Wettability of keratin fiber surfaces, j. Soc. Cosmet.Chem.,28, 273-284 (1977). (21) H-D Weigmann and Y. K. Kamath, Modificationof humanhair throughfiber surfacetreatments: Characterization by wettability,Cosmet. Toilerr.,101, (1986).
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