CurlChemist takes a close look at polyquats, and which are best for curls

Polyquats are of major interest to curlies, specifically the removal of polyquats for those who avoid sulfate cleansers. Build up of any moisturizing or styling agent is a genuine problem because it can lead to limp curls, frizzy hair with a straw-like texture — and it can even lead to permanent damage in the form of breakage. For this reason, I persistently search for publications of studies done that specifically investigate this topic.

Polyquats (polyquaternium) are polymers frequently used in hair-care products to provide conditioning benefits to the hair. The trait they all share is that they are very large molecules with periodic positive charges located at different sites along the molecule. There are many different types of these cationic polymers, with widely varying molecular structures and charge densities (amount of positive charge/molecule). Each specific type of polyquaternium molecule is assigned a numeric designation, such as polyquaternium-4 or polyquaternium-11.

Some of these molecules are linear, like a snake or a single piece of spaghetti, while others have many branches like a tree. Most are fairly high molecular weight (in the 500,000 — 1,000,000 grams/mole range), which imparts the maximum conditioning benefits. A few of the polyquats are obtained via chemical modifications of naturally-derived polymers such as guar gum and cellulose. However, the majority are completely synthetic molecules developed and tested in laboratories, typically copolymers of various monomers selected to give the polymer the final desired properties. (If one is interested in further study, these monomers are often one of the following: vinyl pyrrolidone (VP), diallyl dimethyl ammonium chloride (DADMAC), dimethylaminoethyl methacrylate, and quaternized vinylimidazole (QVI).)

A BASF research group based in Germany published findings of a study they performed to compare the performance of several different common conditioning polyquats. They used several different test methods and sensory feedback tests to compare conditioning effectiveness and how easy it will be to remove removability of a common group of cationic polymers, including cationic guar gum, polyquaternium-7, polyquaternium-10, polyquaternium-11, and polyquaternium-44.

To determine conditioning effectiveness, they measured wet comb-ability of hair treated with each formula. (Wet comb-ability measures the forces required to comb through wet hair after application of the conditioning agent). They also surveyed consumer texture/sensory feedback on each type of polymer (typically accomplished in a small hair salon on site, where volunteers try different products on their hair and report how it feels to them). Atomic force microscopy was used to determine residual polyquat quantity on the hair after rinsing or washing with an anionic surfactant (such as sodium laureth sulfate).

The chemists reported that polyquaternium-44 led the pack by exhibiting superior conditioning benefits while simultaneously resisting build up. Cationic guar gum had the poorest performance in both regards. Polyquaternium-10 did not do as well in the conditioning efficacy analyses, but proved to also be easily removable. Polyquaternium-7 and polyquaternium-11 were somewhere in the middle of the group.

There were several interesting things to be gleaned from the behavior of polyquaterium-44. This is a completely synthetic, branched copolymer, of fairly high molecular weight, and fairly low charge density. Branched polymers like this are more coiled when in aqueous solution, unlike the more extended conformation adopted by their linear counterparts. For this reason, they are more easily deposited onto the surface of the hair, where the positively charged moieties bind to the protein surface.

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Figure 1. Conformation of two different polymer structures in water — a linear polymer on the left and a branched polymer on the right.

The BASF chemists hypothesize that because of the low charge density of this particular polymer, much of the structure actually extends away from the hair surface in loops and coils. These little wiggly bits would act to reduce friction between adjacent hairs, which would reduce tangling and increase ease of comb-ability. This configuration is also credited with how easy it is to remove with a water rinse or shampoo rinse. Many cationic polymers resist removal with even the most harsh shampoos, so this is very interesting behavior.

Another research and development group observed similar behavior with a high molecular weight, branched and lightly crosslinked cationic polymer. This polymer displayed conditioning benefits superior to other cationic polymers when used in relaxer solutions. The inventors discussed data that supports that this polymer penetrated the hair cuticle due to its being open during the chemical relaxing process. Once inside, they believe it formed an elastic cushion inside the hair that provided lasting strength and elasticity to the hair. They also found that this crosslinked, non-linear material was more readily removed from the hair surface than other types of cationic conditioners, which also supports the findings of the BASF group.

The take-home message of this article is that products containing polyquat-44 will give you the best results compared to those formulated with other types of cationic polymers. It provides fantastic detangling and moisturizing benefits and detaches from the surface of the hair easily. Products with polyquat-10 are also a pretty safe choice for those on low-shampoo plans. It would be wise to keep in mind though that other polyquats as well as positively-charged silicones such as amodimethicone may be much more difficult to remove from your hair. As always, your mileage may vary, so don't be afraid to experiment with products and ingredients!


Sources:

Hössel, Dieing, Nörenberg, Pfau, & Sander (BASF Aktiengesellschaft, Ludwigshafen, Germany), Conditioning Polymers in Today's Shampoo Formulations; Efficacy, Mechanism and Test Methods, International Journal of Cosmetic Science, Vol. 22, No. 1, pg. 1-10, 2000

Woodruff, John, Formulators; it is time to widen your horizons, Paper given before the Society of Cosmetic Scientists, Chepstow, 2000

Agent: Joann Villamizar Ciba Corporation/patent Department - Tarrytown, NY, US
Inventors: Emily Crisp Bazemore, Rhonda F. Tsotsoros, Zhiqiang Song, Jianwen Mao
USPTO Application #: 20080138307, Use of high molecular weight crosslinked, water-soluble cationic polymers in hair care formulations


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