Cationic Compounds in Cosmetics

The Good, The Bad, The Weird (And the extremely long-winded post)

Here I’m referring to 2 classes of chemicals: quaternary cationic surfactants and cationic polymers. First off, cationic means something has a (net) positive charge (+). Hair has a net negative charge at the pH environment in which it usually exists (somewhere between pH 4.5 and 5 is average). This charge is mostly because of it’s composition, although damaged hair has more potential bonding sites (negative charges) than less-damaged hair.

I fear I’m about to give the impression that these ingredients are bad for your hair. They are not, in fact, they are responsible for silky, smooth, lustrous hair that holds a style. They help define waves and curls and protect damaged hair/protect hair from damage. They can prevent flyaway hair and the high fluff/frizz factor that comes with wavy and curly hair. What? You have straight hair that frizzes? Then no, you don’t have completely straight hair – you have some waves. These ingredients can be more of a problem for people who do not shampoo their hair often, or who have fine, soft hair, but as you’ll find, shampooing and cationic products is a goofy bit of chemistry.

Quaternary cationic surfactants (and cationic polymers) are the real “conditioners” in hair and skin products. They bond to hair (and skin), whereas most other ingredients in, say, a conditioner are emulsifiers (mix oil and water), thickeners, emollients (oils) moisturizers. These may soften and even penetrate the hair, but they don’t bond to the hair shaft.

Most of us played with magnets in school when we were kids. You’ll recall that the “positive end” of a magnet would attract the “negative end” of another, but repel other positive ends. Opposites attract, likes repel. Thus a cationic (positively charged) conditioner has an electrostatic interaction with your negatively charged hair and it sticks to it (adsorbs). Cationics also resist rinsing off both while wet (as in freshly-applied conditioner) and after drying.©Science-y Hair Blog 2013

Having those ingredients in a formula reduces damage-provoking friction, with the end result of stronger hair.  But have you ever combed your hair or, for wavy and curly-haired people, scrunched or just touched your hair and noticed that your hair was repelling itself? As though you rubbed your head with a balloon? Wavy Library blogger Pedaheh coined the brilliant phrase, “conditioner cling” to describe this phenomenon. Like static-cling-y clothes just out of the dryer. This happens frequently with fine hair, which has a lot of surface compared to its inner bulk and therefore holds a lot more conditioner relative to its weight than does a thicker hair. How are cationic ingredients involved?©Science-y Hair Blog 2013

Quaternary Cationic Surfactants:©Science-y Hair Blog 2013

Quaternary cationic surfactants include ingredients such as Behentrimonium chloride, Behentrimonium methosulfate, Cetrimonium bromide, Cetrimonium chloride, Stearalkonium chloride, Dicetyldimonium chloride, Guar hydroxypropyltrimonium chloride, Stearamidopropyl dimethylamine, Brassicamidopropyl dimethylamine. Most of these are not water soluble, with the exception of the 2 Diemthylamines - which is a designation for the person in the lab, not for you and your hair. Keep in mind that conditioner is a mixture of water and oil-based things, kept together with emulsifiers. So like with salad dressing - there are some water-soluble ingredients (like vinegar) and some water insoluble ingredients (like oil). The end product is not determined by a single ingredient!

Imagine magnets – the positive end of the quaternary cationic surfactant bonds to the negative hair. The thing is, it’s a pretty tight grip. Think giant magnets. Electromagnets that are used in scrap metal yards. This is known as “substantivity” in cosmetics chemistry.©Science-y Hair Blog 2013

Having these ingredients on your hair is not a problem in itself. Not unless you begin to find your hair weighed down, not curling if it should, or repelling itself. Shampooing is not always a solution because most shampoos are based on anionic (negatively charged) surfactants. And now you’re saying, wait, that should mean that it should remove the cationic stuff because it has a negative charge and opposites attract. Yes! But the hair holds the cationics too tightly. The shampoo (anionic) may not be a big enough “magnet” to remove the cationic (conditioner or polymer).©Science-y Hair Blog 2013

Which ingredients are “stickier?” Cetrimonium chloride, in low concentration, is thought to be less tenacious than other quaternary cationic surfactants, whereas Cetrimonium bromide is considered highly substantive to hair. Behentrimonium methosulfate (hey allergy people – Behentrimonium is usually made from canola oil, so unless you’re allergic to mustards, it may work for you) is highly substantive to hair, as is Behentrimonium chloride. You may dislike an ingredient in one formulation and love it in another. The chlorides exhibit especially great substantivity to hair as demonstrated by not rinsing out, by prevention of fading in colored (dyed) hair, and by reducing the force needed to comb hair. But is this simply because the “methosulfates” are relative new kids on the block and haven’t been compared much side-by-side?  Could be.©Science-y Hair Blog 2013

Stearamidopropyl dimethylamine, Brassicamidopropyl dimethylamine - the claims made for these ingredients is that they condition without build-up. But they do bond to hair.  They offer good wet-hair detangling, but are less helpful for dry-hair combing. Meaning if you left a lot in your hair, it might feel a dry or tangly. Conditioners with just this active ingredient tend to add less "weight" to hair (depending on the formula!). That doesn't mean it rinsed out better, it's the nature of the ingredient and the product. The molecular weight and structure is smaller/more compact than Behentrimonium chloride, (for example), and that may mean (just as a mental image) when it's bonding to damaged areas it is working on a slightly smaller scale - covering rough cuticle edges with a smaller patch.

 ©Science-y Hair Blog 2013

Cationic Polymers:

Cationic Polymers include polyquaterniums (Polyquaternium-4, Polyquaternium-10, for example). These ingredients are very often water-soluble, but that’s not terribly relevant for us on the product-using end because they also get a tight grip on hair and so they don’t rinse off. Polyquaterniums are used in shampoos and conditioners to provide lightweight conditioning and frizz-prevention and used in hair styling products because they form stiff films over the hair to provide firm hold. They can add body to fine hair because of their hold/fixative-providing and film-forming behavior.©Science-y Hair Blog 2013

Polyquaterniums are lightweight, but can lead to build-up. Your gel may feel as though it rinsed out, but you’re left with microscopic cationic “soil” (residue) in your hair.

Polyquaternium 4 gives strong hold and may be easier to remove than Polyquaternium 10 or 11, in other words, it is more possible to pry it off with water and a detergent. Certain proteins and quaternary cationic surfactants can bond more firmly with hair than does polyquat-4. There are many other Polyquaterniums (with other numbers following them -7, 37, 44, 67…), all of which will bond more or less tenaciously to hair. Polyquaternium 10 may also be easier to remove than some of the others, there is even a “low residue” version of this polymer available, although it is doubtful that this distinction would be revealed in an ingredient list.

Concentration is important. The more polymer there is, the more the possibility for build up. If you are looking at a product with 20 ingredients and a Polyquaternium is ingredient #15, there isn’t much in there. But if it is ingredient number 3 or 4, there is more present. And even that is misleading because the actual percentage could be pretty low. So it’s best to judge by whether or not you get consistently good results from a product.©Science-y Hair Blog 2013

How to Deal With Build-Up
Using an anionic shampoo (such as Sodium laureth sulfate or Ammonium laureth sulfate) may not do a very good job of removing cationic “soil” and the presence of cationic soil may increase anionic build-up on your hair. If you have a serious feeling of build-up and shampoo makes it worse, read the ingredient list very carefully because...

©Science-y Hair Blog 2013

Alkyl sulfates or alkyl sulfonates are anionic, but are better at removing cationic soils than other “sulfate” detergents (this has been demonstrated through controlled testing). For example, C14-16 olefin sulfonate detergents. These are deep-cleaning detergents, but can be diluted with water for a milder product. 

Additionally, Sodium lauryl sulfate and Ammonium lauryl sulfate, on the other hand, are anionic "sulfate," detergents but may do a better job of removing cationic soils than their laureth-sulfate counterparts because the molecules are smaller, more likely to penetrate hair and therefore more "stripping."

So if you experience conditioner cling, you find your ployquaternium-containing gel stops working wonderfully for you, or your hair gets limp or greasy with too much conditioning, what can you do?

1) Switch shampoos to use different detergents, or switch to styling products that don't feel like they leave residue.

©Science-y Hair Blog 2013

2) Use a light touch with conditioner and look for conditioners in which cationic surfactants are not at the beginning of the ingredient list. Avoid conditioners with heavy doses of oils and “butters” like shea butter.

©Science-y Hair Blog 2013

3) Look for shampoos including Sodium polystyrene sulfonate. This ingredient helps remove 25% more cationic soil than rinsing or shampooing (even with a “sulfate” shampoo).

©Science-y Hair Blog 2013

4) If you are only rinsing your hair and scalp between shampoos, skip conditioner on some occasions if you don't need it for detangling.

Shampoos with Sodium polystyrene sulfonate:

Pure & Basic Clarifying (Lite) Citrus Shampoo

John Frieda Blonde Highlight Activating Shampoos

Pureology Serious Colour Care Purify Shampoo

Alterna LIFE Solutions Clarifying Shampoo

Carol's Daughter Rosemary Mint Purifying Shampoo

  

Sources:

J. Soc.Cosmetic Chem.,43, 259-273 (September/Octobber 1992)

J. Soc.Cosmetic Cthem.,40, 205-214 (July/Augus 1989)

Removal of Cationic Buildup From Keratin Surfaces By Sodium Polystyrene Sulfonate

Presented at PCIA Shanghai - March 2002