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)