by Tonya McKay
Silicones have many unique properties that make them a preferred ingredient for hair care product formulators. They form a film on the surface of hair strands which allows them to effectively act as a lubricant between adjacent hair strands and reduce the forces required for detangling hair. Due to their high refractive index, they also impart a high degree of gloss and shine to hair when used in conditioners and styling products. Silicones also provide protection from the thermal damage often sustained during hair drying and heat styling. Certain silicones, especially amine-functionalized ones, have also been shown to increase color retention of artificially dyed hair.
However, despite their numerous benefits, curlies are frequently admonished to minimize use of silicones or to avoid them entirely.
So what’s the problem?
Sadly, there can be too much of a good thing. Years ago, it was fashionable for stylists to douse curly hair in heavy silicone oils in order to get control of frizz and to add a much-coveted shine to curls. Unfortunately, these products had a tendency to backfire over time. With repeated use, the serums accumulated on the surface of the hair, keeping water from entering the cortex and causing it to become dehydrated, weighing down hair, and completely disrupting natural curl pattern. The buildup could be very difficult to remove, requiring repeat applications of harsh shampoos. The result was dry, frizzy hair that resisted attempts to restore its natural beauty.
Similar results can occur when conditioners with high amounts of non-water soluble dimethicone are used. Buildup issues are especially problematic when non-traditional methods of cleansing are employed, such as conditioner cleansing, baking soda scrubs, or vinegar rinses. For this reason, it has become a popular recommendation for curly-haired people to avoid products containing silicones. This has the unfortunate consequence of depriving many curlies of some of the beneficial properties of silicones in hair care products.
Is There a Solution?
Happily, polymer chemists have spent time developing and optimizing water soluble silicone-based polymers for various reasons. These materials impart many of the desirable properties of ordinary silicone polymers, but they are more easily removed from the hair via rinsing, conditioner washing, or cleaning with mild shampoos, and do not require the use of harsh sulfate-based surfactants. They can also enhance moisturizing properties or add humectant qualities. These silicones provide more options to curly ladies and gentlemen.
What makes a silicone-based polymer water soluble?
Simple silicone polymers, such as dimethicone (polydimethylsiloxane) are comprised of a linear inorganic backbone of silicone and oxygen, with organic (carbon-based) pendant groups. These materials are extremely hydrophobic oils. However, several different types of chemical reactions can be utilized to add hydrophilic character to the polymers. These new polymers are amphiphilic, containing both hydrophobic and hydrophilic portions, and are classified as silicone surfactants.
Perhaps the most straightforward and popular method for rendering a silicone molecule water soluble is by adding multiple units of ethylene glycol (-OCH2CH2O-) to sites along the polymer chain. The oxygen atoms in these segments add polarity to the silicone and are readily available for association with water molecules. This process is called ethoxylation or polyethylene glycol (PEG)-modification.
PEG-modification can be done on sites that dangle from the silicone backbone, which results in a polymer shaped like a comb with hydrophilic tendrils. PEG can also be added to the terminal ends of the silicone polymer, making a straight chain surfactant type copolymer, with a hydrophilic block-hydrophobic block-hydrophilic block structure. Star-like molecules can be created by PEG-substitution occurring both at the ends of the polymer and on the pendant groups. Each type of polymer has slightly different properties.
On product labels, these polymers were formerly denoted by the name dimethicone copolyol. The preferred nomenclature for the comb-shaped polymers now is PEG-X dimethicone, with X being the number of repeat units of ethylene glycol. The block copolymers are designated Bis-PEG-X dimethicone, and the star-shaped polymers are designated Bis-PEG-X/PEG-X dimethicone. The higher the number “x” is, the greater the water solubility. Below a threshold of approximately PEG-6, the polymer is only sparingly soluble, and when the degree of ethoxylation equals or exceeds 8, the material can be considered to be highly water soluble.
Similar modification of a different silicone results in the novel polymer Bis-PEG-18 methyl ether dimethyl silane, which is completely water soluble and highly moisturizing to skin and hair. Another interesting water soluble silicone polymer is one modified with side chain copolymers of poly glucosides (sugars), PEG-8-PG-coco glucoside dimethicone. This material is completely water soluble, has high substantivity to hair and skin, is very moisturizing, and also has sufficient surfactant qualities that it can be used as a foaming agent and mild cleanser in gentle shampoos. Silicone phosphate esters (INCI name: Dimethicone PEG-X phosphate) are another category of water soluble silicone surfactants that provide excellent moisturizing properties and act as foam boosters.
What should I look for on labels?
Ultimately, it is most important to be your own scientist and try various products on your own hair in order to determine what gives the results that you like the most. What works for one person may not work for another, for many reasons.
If you are interested in trying some of the benefits of silicone-based products, but find it important to stick to those that are most easily removed via no-shampoo and mild-shampoo techniques, you will need to know what to look for on labels. The following silicones should be compatible with that type of hair care routine, and should provide many of the desirable effects of silicones, such as the addition of shine, moisturizing effects, thermal protection, and color retention, without any accompanying worries about buildup and frizz..
- PEG-8 (or higher) Dimethicone
- Bis-PEG-8 (or higher) Dimethicone
- Bis-PEG-8/PEG-8 Dimethicone
- Bis-PEG-18 methyl ether dimethyl silane
- PEG-8-PG-coco glucoside dimethicone
- Dimethicone PEG-X phosphate
- Dimethcione copolyol (this is an older and less descriptive designation, but may still be found on some labels)
So curlies, are you willing to let your hair make friends with these water-soluble silicones?