Paper 003 Disc
International Journal of Cosmetic Science, 22 1±10 (2000)
Conditioning polymers in today's shampoo
formulations ± efficacy, mechanism and test methods
P. HOÈ SSEL, R. DIEING, R. NOÈ RENBERG, A. PFAU, R. SANDER
BASF Aktiengesellschaft, Ludwigshafen, Germany
Keywords: atomic force microscopy; cationic polymers; conditioning shampoos; polyquaternium 44
The paper was presented at the IFSCC Sept. 98 in Cannes. Poster No. 110.
Synopsis
Today's shampoo formulations are beyond the stage of pure cleansing of the hair. Additional benefits are
expected, e.g. conditioning, smoothing of the hair surface, improvement of combability and lather creaminess.
Cationic polymers play an important role in providing many of those features. Therefore, within the last few years
Ahed
their use in shampoos has increased greatly.
In the only last two decades, shampoo designation has gradually changed from `2-in-1' to `3-in-1' and then to Bhed
`multifunctional', as at present. The consumer demands products which live up to their promises. Modern Ched
shampoos contain a wide variety of ingredients such as co-surfactants, vitamins and pro-vitamins, protein
Dhed
derivatives, silicones, natural-based plant extracts and other `active ingredients', but there is still a need for
Ref marconditioning polymers.
The specific objective of this study is to assess the conditioning efficacy of cationic polymers and to investigate ker
their mechanisms in a shampoo system.
Fig marThe investigations were carried out on formulations that contained sodium lauryl ether sulphate and different ker
cationic polymers, e.g. Polyquaternium 7, 10, 11, cationic guar gum and Luviquat Care (Polyquaternium 44), a
Table
new branched copolymer of vinylpyrrolidone (VP) and quaternized vinylimidazolium salts (QVI).
We used test methods relevant to the applications in question, such as combing force measurements, the feel of marker
the hair and the creaminess of the lather, to assess the efficacy. Atomic force microscopy and electrokinetics Ref end
Ref start
(streaming potential) were used to detect polymer residues on treated hair.
All the polymers under investigation improved the overall performance of the shampoo formulations. This was
demonstrated by means of combing force measurements, sensorial tests and analytical methods, namely zeta
potential measurement and atomic force microscopy.
Polyquaternium 44 exhibited the best conditioning properties on wet hair without sacrificing removability or
absence of build-up. The latter are the most striking weaknesses of cationic Guar Gum-based polymers.
Polyquaternium 10 can also be removed from the hair after rinsing with anionic surfactant but it does not
perform as well as Polyquaternium 44 in the fields of wet combability and sensorial criteria such as lather
creaminess and feel of the hair.
We postulate that the outstanding properties of Polyquaternium 44 as a conditioning agent for shampoos are
due to its tailor-made `branched' structure.
There is a clear correlation between the molecular weight and the efficacy of the new copolymers of VP and
QVI. Only cationic polymers with a very high molecular weight are effective as conditioners in shampoos based
on anionic surfactants. Surprisingly, they do not have to have a high cationic charge.
On the basis of all our results, our postulation is that the polymer residue which is responsible for conditioning
does not form a flat layer on the hair. Rather, the polymer residue adsorbs with the few cationic moieties, while
the uncharged part of the polymer forms loops, which are orientated away from the hair and which are
responsible for the reduced friction between hairs.
*To whom correspondence should be addressed at: BASF Aktiengesellschaft, 67105 Ludwigshafen, Germany.
Tel: + 49 62 141663; fax: +49 62 197370.
0142-5463 # 2000 International Journal of Cosmetic Science
Paper 003 Disc
2
HoÈssel et al.
ReÂsumeÂ
Les formulations actuelles de shampoing font plus qu'un simple nettoyage des cheveux. On en attend un inteÂreÃt
suppleÂmentaire, par exemple apreÁs-shampoing, lissage de la surface du cheveu, ameÂlioration de la coiffabilite et
aspect creÂmeux du savon. Les polymeÁres cationiques jouent un roÃle important dans l'apport de nombre de ces
caracteÂristiques. Par conseÂquent, ces quelques dernieÁres anneÂes leur utilisation a consideÂrablement augmente dans
les shampoings.
Dans les seules deux dernieÁres deÂcades, l'appellation du shampoing est progressivement passeÂe de ``2 en 1'' aÁ ``3
en 1'' puis ensuite aÁ ``multifonctionnel'', comme actuellement. Le consommateur recherche des produits qui
tiennent leurs promesses. Les shampoings modernes contiennent une grande diversite d'ingreÂdients tels que des
co-tensioactifs, des vitamines et des provitamines, des deÂriveÂs de proteÂines, des silicones, des extraits aÁ base
de plantes naturelles et autres ``ingreÂdients actifs'', mais il existe toujours un besoin pour des polymeÁres
d'apreÁs shampoing.
L'objectif speÂcifique de cette eÂtude est d'eÂvaluer l'efficacite comme apreÁs-shampoing de polymeÁres cationiques
et de rechercher leurs meÂcanismes dans le systeÁme de shampoing.
Les recherches ont eÂte meneÂes sur des formulations qui contiennent du sulfate de lauryl eÂther sodium et
diffeÂrents polymeÁres cationiques, par exemple du Polyquaternium 7, 10, 11, de la gomme de guar cationique et du
Luviquat Care (Polyquaternium 44), un nouveau copolymeÁre ramifie de vinylpyrrolidone (VP) et de sels
quaternaires de vinylimidazolium (QVI).
Nous avons utilise les proceÂdeÂs de controÃle approprieÂes aux applications en question, tels que les mesures de
force de coiffage, le toucher du cheveu et l'aspect creÂmeux du savon, pour eÂvaluer l'efficaciteÂ. La microscopie
atomique et l'eÂlectrocineÂtique (potentiel d'eÂcoulement) ont eÂte utiliseÂes pour deÂtecter les reÂsidus de polymeÁre sur le
cheveu traiteÂ.
Tous les polymeÁres eÂtudieÂs ameÂliorent le comportement global des formulations de shampoing. Ceci est
deÂmontre au moyen des mesures de force de coiffage, des tests sensoriels et des meÂthodes analytiques, en
l'occurrence la mesure du potentiel zeÃta et la microscopie atomique.
Le Polyquaternium 44 preÂsente les meilleures proprieÂteÂs d'apreÁs-shampoing sur cheveu mouille sans diminuer
sa capacite d'eÂlimination ou l'absence d'accumulation. Ces dernieÁres sont les faiblesses les plus frappantes des
polymeÁres aÁ base de gomme de guar cationique.
Le Polyquaternium 10 peut aussi eÃtre eÂlimine du cheveu apreÁs rincËage avec un tensioactif anionique mais il ne se
comporte pas aussi bien que le Polyquaternium 44 dans les domaines de la coiffabilite aÁ l'eÂtat mouille et des
criteÁres sensoriels tels que l'aspect creÂmeux du savon et du toucher du cheveu.
Nous supposons que les proprieÂteÂs exceptionnelles du Polyquaternium 44 comme agent apreÁs-shampoing pour
shampoings sont dues aÁ sa structure ``ramifieÂe'' concËue sur mesure.
Il existe une correÂlation claire entre le poids moleÂculaire et l'efficacite des nouveaux copolymeÁres de VP et QVI.
Seuls les polymeÁres cationiques avec un poids moleÂculaire treÁs eÂleve sont efficaces comme apreÁs shampoings dans
des shampoings aÁ base de tensioactifs anioniques. Etonnamment, ils n'ont pas besoin d'avoir une charge
cationique eÂleveÂe.
Sur la base de tous nos reÂsultats, notre hypotheÁse est que le fragment de polymeÁre qui est responsable du
traitement ne forme pas une couche plate sur le cheveu. Le fragment de polymeÁre adsorbe plutoÃt les quelques
fragments cationiques, tandis que la partie non chargeÂe du polymeÁre forme des boucles, qui sont orienteÂes aÁ
l'exteÂrieur du cheveu et qui sont responsables de la friction reÂduite entre les cheveux.
Introduction
There is still a need for conditioning polymers in today's shampoos, which may contain a
wide variety of ingredients such as co-surfactants, vitamins and pro-vitamins, protein
derivatives, silicones, natural-based plant extracts and other `active ingredients'.
Conditioners are claimed to improve many hair attributes, e.g. combability, feel,
softness, shine, resistance to damage and reduction of split ends, as well as improving the
creaminess of the lather.
Even in small amounts, cationic polymers in particular play an important role in
providing many of these attributes in shampoo formulations. Typical concentrations are in
the range of 0.1% for normal hair to 0.5% for damaged hair. It is also known that several
0142-5463 # 2000 International Journal of Cosmetic Science
Conditioning polymers
3
cationic polymers can build up on the hair to an undesirable extent. Thus, the removability
of these compounds from the hair is also an important factor for the consumer.
Conditioning polymers in shampoos act by precipitating onto the hair when the
shampoo is rinsed out [1] (Fig. 1).
The coulombic attraction between the anionic functions of the surfactant and the
cationic groups of the polymer results in a formation of a charge-neutral complex, which is
charge neutral at a certain concentration ratio. However, at concentrations used in practice
a large excess of anionic surfactant leads to a soluble complex in which the cationic polymer
charge is overcompensated. Only certain types of cationic polymers (see below) precipitate
when the shampoo is diluted below the critical micelle concentration of the surfactant. This
occurs in the rinsing process after washing the hair with the shampoo concentrate (dilutionprecipitation mechanism) [2]. The mechanism by which the cationic polymer is adsorbed
onto the hair in the presence of excess anionic surfactant is still not entirely clear.
Objective of the study
The purpose of this paper is to assess the efficacy of cationic polymers by means of
appropriate test methods and to investigate the deposition mechanism of cationic
conditioning polymers in shampoos using the new Polyquaternium 44 as a model
conditioning polymer.
The investigations were carried out on formulations that contained sodium lauryl ether
sulphate (SLES)/cocamidopropyl betaine and selected cationic polymers which are known
to be effective conditioning polymers in shampoos:
. Polyquaternium 7
. Polyquaternium 10
Figure 1. Precipitation of cationic polymers in shampoos.
0142-5463 # 2000 International Journal of Cosmetic Science
4
HoÈssel et al.
. Guar Hydroxypropyltrimonium Chloride (GHPTC)
. Polyquaternium 44 (Luviquat Care1)
Chemically, Luviquat Care1 is a new branched copolymer of vinylpyrrolidone (VP) and
quaternized vinylimidazolium methyl sulphate (QVI), which is branched and exhibits a
very high molecular weight of about one million.
We used test methods relevant to the applications in question, such as combing force
measurements, the feel of the hair and the creaminess of the lather, to assess the polymer's
efficacy. Physical measurements, e.g. atomic force microscopy (AFM) [3±6] and electrokinetics (streaming potential) [7,8] were used to detect polymer residues on treated hairs.
Experimental
Combing force measurements
Wet combability measurements were performed on medium bleached swatches of Caucasian
hair by means of an Easy-Test 86802/E tensile tester. Dry combabilities were measured on
virgin Asian hair swatches by means of a Diastron MTT 160 miniature tensile tester. After
shampooing for 1 min, the hair was rinsed with water for 1 min under standard conditions (1
min/388C). Each polymer was tested on at least 10 different hair tresses. The reduction in
combing force was calculated by Equation (1). Standard deviations were below 10%.
DC = 100±(xM * 100/xB)
(1)
DC = reduction in combing force (%)
xM = mean square of combing work after treatment (mJ)
xB = mean square of blank value (mJ)
Feel of the hair and lather creaminess
The feel of the hair and the lather creaminess was assessed subjectively by an experienced
test panel of five technicians and rated as very good (1), good (2) or poor (3).
Streaming potential measurements
The streaming potential measurements were performed with a Paar EKA electrokinetic
analyser. The electrolyte flows through the measuring cell filled with the finely cut Asian
hair (approx. 4 g) and the resulting streaming potential was measured across the Ag/AgCl
electrodes parallel to the flow of the electrolyte. The electrolyte is circulated in a closed loop
system by a microprocessor controlled rotary-vane pump. In the experiments, the streaming potential and the pressure drop across the sample were continuously recorded. The zeta
potential was calculated from the slope. The error limit lies in the range of + 5 mV.
The effects of surface conductivity and plug porosity were accounted for by the method
of Fairbrother and Mastin [9].
In a typical preparation, 4 g of virgin Asian hairs was treated with the polymer (0.5%)/
SLES (14.0% active) formulation in a 100-ml beaker, rinsed as described above and
transferred to the measuring cell. The zeta potential was measured at an electrolyte
concentration of 1 mM KCl at pH 7 (10 cycles).
After rinsing the measuring cell with water, the hairs were removed, treated with SLES
(40 ml, 14% active) and rinsed with water. The hairs were then transferred to the
measuring cell and the zeta potential was measured again.
0142-5463 # 2000 International Journal of Cosmetic Science
Conditioning polymers
5
Atomic force microscopy (AFM)
AFM tapping mode images were recorded with a Nanoscope Dimension 3000 SPM
(Digital Instruments, Santa Barbara, CA) using Si cantilevers (35 N m71, approx. 300
kHz, Nanoprobe).The same cleaned Asian hairs were used as described above. Single hairs
were fixed in a special cell and scanned. After treatment of the fixed hair with polymer
(0.5%/SLES 14.0% active), as described above, AFM images were recorded after one and
after five treatments. The single hairs were then washed with SLES solution (14.0% active)
for 1 min and rinsed with water for 2 min. Treating the hairs in this special cell made it
possible to scan exactly the same part of the hair each time and avoid errors due to different
hair quality. Changes on the surface of the hair after different treatments could therefore be
confidently attributed to residues of polymer or a polymer/surfactant complex.
The cell has an inlet at the front and an outlet on the back, so it can be filled up
with liquid and drained in the microscope (Fig. 2). The hair sample is placed on the
black water-resistant adhesive tape (black circle) on an elevated area on the bottom of
the washing cell. The D3000 is a scanning tip system, so the optical system and the
piezo-scanner is integrated in the steel pipe coming from above. From the left, an optical
video microscope, which is needed for the coarse positioning, is directed at the sample.
The bright spot visible at the sample position is the illumination necessary for the
optical microscope.
Figure 2. Nanoscope D3000 SPM with a home-built washing cell.
0142-5463 # 2000 International Journal of Cosmetic Science
6
HoÈssel et al.
First the hair is mapped in the dried state. Then it is treated and finally the solution is
pumped out into the waste. After drying, the same spot of the hair is mapped again. As the
arrow indicates, if needed, this cycle can be repeated (Fig. 3). A blank using water showed
that the swelling does not influence the structure of the hair in the dry stage [10].
Results and discussion
The reduction in wet combing force of about 50% and 40% achieved with concentrations
of 0.5% Polyquaternium 44 in the shampoo formulations and 0.1%, respectively, is
outstanding (Fig. 4). At concentrations as low as 0.1% the superiority of Polyquaternium
44 is even more pronounced.
Figure 3. Treatment scheme for hair in the washing cell.
Figure 4. Wet combability.
0142-5463 # 2000 International Journal of Cosmetic Science
Conditioning polymers
7
It was possible to demonstrate the efficacy of these conditioning polymers by means of
zeta potential measurements (Fig. 5) and AFM (Fig. 6). When the hair is treated with the
test shampoos containing a cationic polymer, the zeta potential changes from±52 mV
(virgin Asian hair) to higher values, but there is no change to positive values, as in the case
of treatment with cationic formulations without anionic surfactant [8]. This indicates that
a charge-neutral polymer/surfactant complex is adsorbed onto the hair. Polyquaternium
44 and Polyquaternium 10 were the only polymers whose residues could be desorbed from
the hair by rinsing with water/surfactant. Polyquaternium 7 and the Cationic Guar Gum
could not be desorbed completely from the hair. This means that shampoo formulations
containing one of these polymers tend to overcondition the hair and to cause build-up.
The AFM investigations clearly underline that Polyquaternium 44 can be removed even
after several treatments with the test shampoo. Figure 6a shows the scales of an untreated
hair, Fig. 6(b) and (c) show treated hairs with residues of polymer/surfactant complex and
Fig. 6(d) hair which was rinsed with water/surfactant. This rinsed hair looks like the
untreated hair depicted in Fig. 6(a).
There is a clear correlation between the solution viscosity and the efficacy of the new
branched copolymers of VP and QVI (Fig. 7). Only cationic polymers with a very high
molecular weight such as Polyquaternium 44 (MW &1 Mio, light scattering) are effective
as conditioners in shampoos based on surfactants. Surprisingly, they do not need to have a
high positive charge.
The advantage of Polyquaternium 44 over other cationic polymers is that it is a very
effective conditioner but can nevertheless be readily removed and does not build up on the
hair. We postulate that this outstanding combination of properties is due to its tailor-made
branched structure (Fig. 8).
A branched polymer is more coiled than a linear polymer and therefore less hydrated in
water-based formulations, e.g. shampoos. Therefore, the polymer/surfactant complex is
more readily precipitated and deposited on the hair upon dilution of the shampoo
Figure 5. Zeta potential measurements.
0142-5463 # 2000 International Journal of Cosmetic Science
8
HoÈssel et al.
Figure 6. Atomic force microscopy images(arrows indicate the same part of the hair). (a) Untreated
hair; (b) hair treated once with the test shampoo (0.5% polyquaternium 44/14.0% SLES) and rinsed
with water; (c) hair treated five times with the test shampoo (0.5% polyquaternium 44/14.0% SLES)
and rinsed with water; (d) hair treated as (c) and rinsed with SLES and water.
formulation (dilution-precipitation mechanism) [1,2] which correlates with a high
efficiency. A coiled polymer is less strongly adsorbed on a surface, e.g. hairs, than a
straight polymer and is therefore much more easily desorbed if necessary.
Summary
Conditioning polymers are still important in today's shampoos. The features and benefits
of this class of polymers are summarized in Fig. 9.
All considered polymers improve the overall performance of shampoo formulations.
This was demonstrated by means of combing force measurements, sensorial tests and
analytical methods, namely zeta potential measurement and AFM.
0142-5463 # 2000 International Journal of Cosmetic Science
Conditioning polymers
9
Figure 7. Correlation between the solution viscosity and the efficacy of VP/QVI copolymers
(reduction in wet combability); Polyquaternium 44 has a solution viscosity of 2500±3500 mPa at 5%
solids).
Figure 8. Structure of Polyquaternium 44.
Polyquaternium 44 exhibits the best conditioning properties on wet hair without
sacrificing the removability. The latter is the most striking weakness of PQ 7 and Cationic
Guar Gum-based polymers.
Polyquaternium 10 can also be removed from the hair after rinsing with anionic
surfactant but it does not perform as well as Polyquaternium 44 in the fields of wet
combability and sensorial criteria such as lather creaminess and feel of the hair.
We postulate that the outstanding properties of Polyquaternium 44 as a conditioning
agent for shampoos are due to its tailor-made `branched' structure.
0142-5463 # 2000 International Journal of Cosmetic Science
10
HoÈssel et al.
Figure 9. Summary of the test results.
References
1. Lochhead, R.Y. Conditioning shampoos. Soap/Cosmet. Specialities for October 1992, 42±49
(1992).
2. Lochhead, R.Y. The history of polymers in hair care. Cosmet. Toilet. 103, 23±61 (1988).
3. Goddard, E.D. and Schmitt, R.L. Atomic force microscopy investigations into the absorption of
cationic polymers. Cosmet. Toilet. 109, 55±61 (1954).
4. HoÈssel, P, Sander, R. and Schrepp, W. Scanning force microscopy. Cosmet. Toilet. 111, 57±62
(1996).
5. Smith, J.R. Use of atomic force microscopy for high resolution non-invasive structural studies of
human hair. J. Soc. Cosmet. Chem. 48, 199±208 (1997).
6. Pfau, A, Hoessel, P, Vogt, S, Sander, R. and Schrepp, W. The interaction of cationic polymers
with human hair. Macromol. Symp. 126, 241±252 (1997).
7. Hunter, R.J. Zeta potential in colloid science ± principles and applications. Academic Press,
London (1981).
8. Ribitsch, V., Jacobasch, H.J. and Boerner, M. Streaming potential measurements of films and
fibers (R. A. Williams, ed.), pp. 354±365. Butterworth Heinemann Ltd, Oxford (1991).
9. Fairbrother, F. and Mastin, H. Studies in electro-endosmosis. J. Chem. Soc. 125, 2319±2330
(1924).
10. O'Connor, S.D, Komisarek, K.L. and Baldeschwieler, J.D. Atomic force microscopy of human
hair cuticles: a microscopic study of environmental effects on hair morphology. J. Invest.
Dermat. 105, 96±99 (1995).
0142-5463 # 2000 International Journal of Cosmetic Science