Technology in the field of cosmetic chemistry is well understood which makes it difficult to develop impactful innovations. From a performance standpoint, there isn’t much room for innovation in the areas of surfactants or emollients. Sure, there are still new compounds to try, but most of the main lines of investigation have been done and it’s unlikely we will find new compounds that lead to consumer perceptible differences for these classes of molecules. Consumers are just not very observant.
But there is still room for new molecule innovation in the cosmetic industry. The most significant innovations will most likely be found in the area of polymers. Currently, our command over polymers is primitive being able to only swap out monomers and adjust ratios. However, much more complex molecules are possible and could prove useful in the creation of cosmetic products. In fact, all of biology is based on proteins and enzymes which are just biopolymers made with different sequences of amino acid monomers.
One kind of polymer that has already found great use in cosmetic formulating are Polyquaterniums.
These versatile polymers offer a variety of benefits when incorporated into cosmetic formulas. Let’s look at the different Polyquats available and discuss some of their properties, functions and uses.
Polyquaternium chemistry
Polyquats are a class of cationic polymers used in both skincare and hair care formulas. They can be derived by chemically modifying natural polymers, such as cellulose, guar or chitosan, through the addition of quaternary ammonium compounds side chains. They can also be created from various organic monomers like acrylamide and diallyldimethylammonium chloride, vinylpyrrolidone and diallyldimethylammonium chloride and others.
However they are made, the resulting polymers will have a long carbon chain with a number of positive charged groups that allows them to bond with the negatively charged surfaces of hair and skin. This characteristic helps the polymer stay on the surface, set up a film and resist rinse-off.
How it works
One of the primary formulation challenges in making hair and skin products is that you need a way to ensure that beneficial ingredients stay on the surface even after the rinse-off phase. Strangely, some shampoos contain ingredients like proteins, vitamins, and oils which are simply washed away during use. Certainly, those might work as good claims ingredients but without a mechanism by which they deposit on the surface, most of it just ends up down the drain.
However, polyquaternium compounds don’t have this problem because they do have two mechanisms through which they can remain on hair even through the washing and rinsing phase. One method is through electrostatic bonding and another is through the dilution/deposition mechanism.
Electrostatic bonding is easy enough to understand. The Polyquat molecules contain numerous positive charges and they are attracted to the negatively charged sites on the surface of hair. This bonding inhibits rinse-off.
The dilution/deposition mechanism works like this.
- Before use: In the product, polyquaterniums are generally highly concentrated. They remain in the solution, evenly dispersed and fully dissolved due to their water-soluble nature.
- During use: When a consumer applies the product to hair or skin and adds water (diluting it), the situation changes. The concentration of the polyquaterniums decreases, altering their behavior.
- Deposition: At a certain concentration, triggered by the dilution, the polyquaterniums become less soluble. They fall out of solution and form a layer (or deposit) on the surface. This layer resists rinse off and remains on the hair.
This remaining polymeric film can provide a number of noticeable benefits.
Benefits of polyquaternium in use
In hair products, there are a number of benefits a polyquat can provide.
Enhanced Conditioning: The polyquaternium film provides noticeable conditioning properties. It smoothens the cuticles, reducing frizz, and improving hair manageability. This results in softer, silkier, and more manageable hair.
Improved Detangling: The cationic nature of Polyquaternium aids in detangling hair by reducing inter-fiber friction. This makes combing easier and helps prevent hair breakage, especially in wet hair conditions.
Style Retention: When used in styling products like mousses, gels, or sprays, Polyquats can help improve style retention properties by maintaining hair shape, volume, and hold, while ensuring longer-lasting styles.
Heat Protection: Polyquaternium polymers may also offer some heat protection. They form a protective barrier on the hair shaft, reducing damage caused by heat-styling tools like blow dryers, curling irons, and straighteners.
Polyquats in Skin Care
Polyquaternium’s use is not limited to hair care alone as it can also be used for various skin care benefits.
Moisturization and Hydration: Some polyquats acts as a humectant, attracting moisture from the environment and binding it to the skin. This helps to improve skin hydration, keeping it supple and reducing the appearance of dryness and fine lines.
Skin Conditioning: The film-forming properties of Polyquats allow them to create a protective barrier on the skin’s surface, minimizing water loss and protecting against environmental irritants. This, combined with occlusive agents, can lead to smoother, softer, and more conditioned skin.
Formulation Benefits
In addition to the performance benefits, polyquaternium compounds can also positively affect a formula. For example, they can provide stabilization of emulsion-based formulas by interacting with both the oil and water phases and preventing separation. This can also improve the overall texture and feel of the product upon application. They can also improve the spreadability of skin care products, allowing for easier application and better coverage on the surface.
Finally, this class of ingredient has been evaluated by the Cosmetic Ingredient Review (CIR) Expert Panel, and are generally considered safe.
Environmental concerns
While polyquats are safe for human use, some are concerned about their impact on the environment. In general, they are not easily biodegradable so may accumulate in the aquatic environment after being washed down the drain. This could potentially pose a risk to aquatic organisms, however, the large molecular size of the compounds makes it less likely. As with most environmental questions, more research is needed in this area.
Commonly used Polyquats
The number after the term polyquat is not related to the chemical structure but rather the order in which the ingredient was registered with the INCI Dictionary. As far as could be found there are over 116 polyquats registered. Here are some that are more commonly used.
Polyquaternium-4: Used in hair styling gels, mousses, and sprays because it offers an improve hold and can form a film on the hair surface.
Polyquaternium-6: A highly cationic conditioner and anti-static agent often used in shampoos and conditioners.
Polyquaternium-7: Commonly used in hair care products for its detangling and hair conditioning properties.
Polyquaternium-10: A cellulosic polymer often found in hair care products, especially shampoos and conditioners, due to its anti-static and moisture-retaining properties.
Polyquaternium-11: Found in hair mousses and lotions as it provides curl retention and volume.
Polyquaternium-37: Often found in hair care products as it can form a film on the hair, providing conditioning benefits.
Polyquaternium-39: Used in hair and skincare products for its moisturizing and conditioning properties.
Polyquaternium-44: Incorporated into a wide variety of cosmetics and personal care products, including hair care and skincare products, due to its ability to form a thin coating on the skin or hair, providing a smooth feel.
As was said early on, there is not a lot of room for molecular innovation in the areas of surfactants and emollients. But polymers can be built one molecular unit at a time. This can lead to emergent properties that aren’t expressed in the individual monomers. For this reason, polymers like Polyquaterniums will be where we find the most significant innovations in cosmetic raw materials in the future.
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