Cationic polymers are widely used in shampoo formulations to provide conditioning benefits such as better hair combing, manageability, frizz control and higher resistance to damage.
1,2 Recently, sensorial benefits imparted by these polymers have become key differentiation attributes in the highly competitive shampoo market. Jaguar C500 is a novel low molecular weight cationic guar derivative (INCI: Guar hydroxypropyltrimonium chloride). It has been designed to help formulators create shampoos that deliver effective conditioning while providing a differentiating sensorial experience compared to that offered by conventional conditioning polymers, such as high molecular weight cationic guar derivatives and polyquaternium-10 polymers (PQ-10). In this study, the conditioning performance and sensorial attributes of Jaguar C500 are determined and compared to those of conventional conditioning systems.
Materials and methods
Materials
• Cationic polymers: Cationic guar derivatives, Jaguar C500, Jaguar C17 and Jaguar C13S were supplied by Rhodia. Cationic hydroxyethyl celluloses (INCI: Polyquaternium-10) were supplied by either Amerchol Corporation (Ucare, trade name) or Rhodia (Polycare, trade name). Polyquaternium-7, a copolymer of acrylamide (AM) and dimethyldiallylammonium chloride (DADMAC) were supplied by Rhodia.
• Surfactants: All the shampoos considered in the study share a common surfactant chassis, consisting of 14 wt% sodium laureth sulfate (SLES) from Empicol ESB 3/M6 supplied by Huntsman and 2 wt% sodium cocoamphoacetate (CAMA) from Miranol Ultra C32 by Rhodia.
• Dimethicone emulsion: For the 2-in-1 shampoos considered in the study, an emulsion of Mirasil DM 500000 (dimethicone from Bluestar Silicone) with an active content of 65% and a submicronic droplet size was used.
• Hair: Except where otherwise specified, hair tresses were supplied by IHIP (International Hair Importers & Products Inc.). Both virgin dark brown Caucasian hair and regular bleached Caucasian hair were used. Hair tresses were washed with a 10% SLES solution prior to being shampooed.
Methods
Shampoos’ production procedure: The shampoos were prepared as follows: add water to the beaker and start agitation. Continue stirring while sprinkling in the cationic polymer. Once the polymer is completely dispersed, adjust pH between 4 and 5 for cationic guar derivatives and above 10 for PQ-10 polymers to ease polymer hydration. Once the polymer solution is uniform, add the CAMA and SLES surfactants in that order waiting for each to dissolve before adding the next. Once homogeneous, add the preservative and adjust the desired viscosity (8000 mPa•s @ 10 rpm) with sodium chloride. Finally, adjust pH to 6.0-6.5 with citric acid. For 2-in-1 shampoos, the dimethicone emulsion was added after the introduction of SLES surfactant.
Polymer substantivity and build-up: Polymer substantivity (i.e. ability of an active to deposit onto a surface and to resist wash-off during shampooing) and build-up (i.e. accumulation of an active onto a surface) were measured indirectly by detecting the amount of Pyrazol Fast Red 7BSW (Sigma Aldrich, CAS 2610-10-8), an anionic tracer which associates with any cationic polymer, and thus binds to shampooed hair once the cationic polymer has effectively been deposited. Shampooed tresses were first exposed to a 0.5 wt% aqueous solution of this anionic red dye. After one minute of rinsing at 38°C, the dye/polymer complex was extracted from hair using a sodium chloride solution. A Perkin Elmer UV/VIS spectrometer (model: Lambda Bio 40) was used to measure the dye characteristic response at 528 nm, from which one can easily deduce the dye uptake (expressed in microgram of dye per gram of hair). For build-up investigations, the dye uptake was measured after 5, 10 and up to 15 consecutive washing cycles.
Wet combing: Hair tresses were combed at 300 mm/min using a MTT 170 Miniature Tensile Tester (Dia-Stron Ltd). Combing force versus displacement curves were obtained in the process. Total combing work (corresponding to the integral of this signal) was extracted. The difference in total work required to comb the hair tress before and after treatment was deduced and generally expressed as a percentage of reduction of combing work. For each for
mulation, five hair tresses were assigned and used to calculate an average percentage reduction of combing work. Silicone deposition: Two methods were used to measure silicone deposition. The first method used X-ray fluorescence spectroscopy which is a non-destructive method carried out directly on the treated hair tresses. The second method consisted of extracting the dimethicone deposited on hair using THF and of dosing the dimethicone amount by GPC using an ELSD (evaporative light scattering detector). The procedure was as follows: treated hair tresses were placed in PET-bottles, and THF was added. After 24 hour mixing, the supernatant was recovered. However, its concentration is generally too low to allow trustworthy detection and it must be transferred to an evaporating dish where THF is totally evaporated. The residual was then resolubilised with a small and known amount of THF and analysed by GPC using THF as the mobile phase. Detection was made by a PL-ELS 100-ELSD detector supplied by Polymer Laboratories. The amount of dimethicone deposited on hair, Q, expressed in ppm (?g of dimethicone per gram of hair) was calculated as follows:
Equation 1: Q (?g of dimethicone per gram of hair) = Cdimethicone x mTHF mhair where Cdimethicone is the dimethicone concentration in the GPC vial expressed in ppm (?g dimethicone per gram of THF), mTHF the amount of THF, expressed in grams, used to re-solubilise the dimethicone in the evaporating dish and mhair, the amount of hair expressed in grams introduced in the polyethylene bottle. The deposition yield is calculated as follows:
Equation 2: R (%) = Cdimethicone x mTHF mshampoo x ??where mshampoo is the amount of shampoo, expressed in micrograms, used to treat the hair tress and ?, the concentration of dimethicone in the shampoo. A minimum of 2 hair tresses were used for each formulation to calculate an average amount of silicone deposited on hair and an average deposition yield. Hair volume and hair bounce: The measurements were outsourced to a private research institute. The hair tresses were obtained from De Meo Bros., New York, NY. Each tress is about 16 g in mass and about 25 cm in length. The tresses were shaped using a mild perming process. Five hair tresses were used for each formulation. The measurements combined the use of Instron equipment and image analysis. The measurements are based on a modified method originally due to Garcia and Wolfram.3 Each hair tress was first equilibrated overnight in a temperatureand humidity-conditioned room (21°C, 65% RH). For each hair tress, four experimental cycles were carried out, each consisting of a combing step to remove any tangles, followed by 3 passes through the confining ring of Instron equipment, which allows for measuring the work (compression energy) required to pull a tress of given volume through a ring of given diameter. After each of the 3 passes through the ring, the average volume of the hair tress is measured using a software driven CCD camera which captures 10 different profiles of the vertically mounted rotating tress in one minute. During each of the four different cycles, the first pull (referred to as Pass 1) is always considered as an initialisation pass that erases the combing and compression history of the tress. For this reason, the compression energy and volume values of Pass 1 are not used in any calculation. On the other hand, Pass 2 is used as the reference pass to determine the average volume and compression energy of a hair tress. Finally, changes in hair volume and compression energy (in %) between Pass 2 and Pass 3 were used to actually evaluate hair bounce. Panel studies: Pairs of virgin dark brown Caucasian hair tresses of 10 g net in mass were distributed to four expert panellists skilled in evaluating sensorial and conditioning properties delivered by shampoos. Each pair consists of one tress assigned to a Jaguar C500-based shampoo and the other tress either to a PQ-10- based, Jaguar C17-based or a polymer-free shampoo (referred to as “polymer-free”). For each pair of shampoos, panellists performed a first evaluation, then shampooed the two hair tresses with a 12% SLES solution, permuted the two hair tresses and performed a second evaluation. Each panellist was asked to evaluate each pair of shampoos giving a total of 8 evaluations for each shampoo in a given pair.
Results and discussion
Figure 1 shows the anionic red dye uptake on hair (hence the level of deposited cationic polymer with which the red dye interacts) when hair has been treated with the Jaguar C500-based shampoo. As of the first application, there is a large increase in the signal, which shows immediate deposition of the active on the surface of hair. Jaguar C500 therefore significantly deposits on hair with a single shampoo application. As the number of applications increases, the signal quickly plateaus to reach a constant level. This shows that the polymer does not build-up with repeated usage and hence does not weigh hair down with multiple washing cycles. As for the conditioning benefits, Figure 2 shows how Jaguar C500 provides wet combing reduction similar to those of polyquaternium-10 polymers (Ucare LR400 and JR400) at the same polymer dosage. Considering that the polyquaternium-10 selling price is noticeably higher than that of Jaguar C500 (a price difference of the order of 40%), Jaguar C500 is particularly well suited for the design of cost-effective conditioning formulations. Aside from its direct conditioning benefits, Jaguar C500 is also able to deposit silicone from 2-in-1 shampoos on both Caucasian and Asian hair as shown in Figure 3. First, we point out that it offers a better deposition efficiency than the polyquaternium-10 polymers tested and a performance level similar to that of polyquaternium-7. In this respect, not only does Jaguar C500 turn out to be a competitive alternative for cost-effective formulations, but it also performs at least as well, or even better than these wellestablished benchmarks, whether these are natural (cellulosic polyquaternium-10) or synthetic (acrylamide/DADMAC copolymer polyquaternium-7). On the other hand, Jaguar C500 shows a smaller deposition efficiency than conventional grades of Jaguar polymers such as Jaguar C17 and Jaguar C13S, often considered as “high efficiency” conditioners. Within the guar-based chemistry, this difference in deposition efficiency may simply result from the difference in molecular weights between these polymers: with its lower molecular weight, Jaguar C500 traps less silicone droplets in the coacervates that form on dilution of the shampoo, thereby leading to a lower amount of silicone deposited on hair. However, Jaguar C500 provides an excellent alternative to these high conditioning polymers, because it offers differentiating sensorial attributes and improved hair body and bounce properties. Hair body measurements carried out by the private research institute (Fig. 4) show that the Jaguar C500-based shampoo offers significantly better volumising ability than either a Polycare 400-based (a polyquaternium-10) shampoo, or even a commercial shampoo claiming amplified volume effect. Compared to Jaguar C500, Jaguar C13S provides similar volume improvement up to 5 washing cycles. However, as the number of cycles becomes too large, Jaguar C13S eventually brings the volume back down, causing the hair tress to weigh down most certainly because of the much larger molecular weight of this high conditioning polymer. Analysing the compression energy data also shows that Jaguar C500 provides hair bounce and that hair bounce is not affected by multiple washing cycles. Note that these hair volume and bounce results are consistent with the data generated with the red dye method, which showed that Jaguar C500 does not build up with repeated usage. Finally, the sensorial benefits provided by Jaguar C500 have been assessed on dark brown Caucasian hair and compared to those of Jaguar C17, Polycare 400 (PQ-10) and a polymer-free formulation. The panellists were asked to assess both foam and hair feel properties. The parameters quantitatively scored are shown in Figure 5. Jaguar C500 provides foam richness enhancement against the polymer-free formulation. Foam appearance is scored qualitatively: panellists have noticed that foam obtained from Jaguar C17 and Jaguar C500 shampoos is much less dull than those coming from the polymer-free and PQ-10 shampoos. Foam is nicer, whiter and shinier with Jaguar polymers. Thus, the lower molecular weight of Jaguar C500 does not seem to negatively impact the foam attributes usually rated as excellent for Jaguar polymers.4 Hair feel during shampooing and the first stages of rinsing with Jaguar C500 are similar to those noticed for the polymer-free formulation, whereas hair is significantly more lubricated with Polycare 400 and Jaguar C17 formulations. Further, in the rinsing, some differences between Jaguar C500 and the polymer-free formulation are perceived. While gliding comes back to the initial level for the polymer-free formulation, Jaguar C500 provides a slight increase in hair glide, yet not as extensively as Polycare 400 and Jaguar C17. Once rinsing is complete, squeakiness is still perceived for hair washed with Jaguar C500 while hair is no longer squeaky when washed with Polycare® 400 and Jaguar C17. Thus, the Jaguar C500-based shampoo allows for cleansing and conditioning hair while keeping a feel similar to that provided by a cleansing shampoo that does not contain any polymer. The feel is not heavy, and hair is still squeaky yet conditioned.
Conclusion
In conclusion, Jaguar C500 is an ideal compromise as a conditioning polymer to make cost-effective shampoos that still deliver satisfactory conditioning benefits, volumising effects with a pleasant lather and hair feel. It is particularly suitable for everyday use, thin hair and volumising shampoos.
Acknowledgements
The authors wish to thank Florence Deschaseaux and Denis Bendejacq from Rhodia for their contribution to the work as well as Florence Bussod, Hedi Modaressi, Tobias Futterer, Irene Wong and Andy Lee from Rhodia for useful discussion and support.
References
1 Schueller R., Romanowski P. Introduction to Conditioning Agents for Hair and Skin in Conditioning Agents for Hair and Skin, Schueller R., Romanowski P. Eds. (Marcel Dekker, New York, 1999), 1-12. 2 Lochhead R., Huisinga L., Waller T. Deposition from Conditioning Shampoo: Optimizing Coacervate Formation, in Hair Care: From Physiology To Formulation, Cosmetics & Toiletries, ISBN: 978-1-932633-35-1, 2008, 115-122. 3 Garcia M.L., Wolfram J.J. Measurement of bulk compressibility and bulk resilience of a hair mass, 10th IFSCC Congress, Sydney, Australia (1978). 4 Chiron S. Performances and Sensorial Benefits of Cationic Guar in Hair Care Applications, in Hair Care: From Physiology To Formulation, Cosmetics & Toiletries, ISBN: 978-1-932633- 35-1, 2008, 183-194.
