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  Figure 1. Simple schematic of a polymer. Imagine that it has millions of the same repeat units.
   
 

  Figure 2. A model of a dendrimer,a “hyper-branched” polymer
   

Polymers can be found in most hair care products, performing a variety of different functions. Shampoos, conditioners, and styling products all rely upon polymers in order to achieve their desired effects. So what are polymers and what is so special about them?

Polymers are very large molecules that are made up of many repeating units of small molecules chemically bonded together. A polymer can be composed of many units of a single type of small molecule (called a homopolymer) or can be composed of many units of two or three different types of small molecules (called a copolymer). Many polymers are found in nature, such as DNA and RNA, spider silk, cellulose (found in cotton fibers, starches, and tree bark, just to name a few places.), proteins, natural rubber, etc. Polymers can also be synthesized in a lab or manufacturing plant to have linear forms, branched forms, and even three-dimensional hyper-branched forms resembling 3-d snowflakes, known as dendrimers.

The neat thing about polymers is that they can be specially made or modified to serve many different purposes, from applications as diverse as structural materials on airplanes and automobiles, bullet-proof glass, bullet-proof vests, time-released drug-delivery agents, temporary bone-replacement or reinforcement in the body, fibers for clothes we wear, super absorbent materials in diapers, paint and coatings for many uses, and also in hair care products.

Conditioning polymers

Cationic polymers are quite popular for use as conditioning agents for the hair. These polymers have been chemically modified to have positive charges along their backbone. Since hair is negatively-charged, these polymers become bound electrically to the surface of your hair when applied in the shower and resist being rinsed off by the water. This causes the cuticles on the surface of your hair to lie flat, which gives a smooth texture and shiny appearance to the hair. It also helps separate and protect each strand from adjacent strands, which prevents tangling and tearing and makes both wet and dry combing easier. These types of polymers, known as polyquaterniums in the INCI naming system, are most often modified versions of naturally occurring cellulose and guar gum.

Silicones are also a highly popular ingredient used by hair care product formulators for conditioning properties. These polymers deposit onto the surface of the hair and act to reduce combing friction, provide an emollient effect, impart gloss and reduce static charge between hair strands.

Examples include:

Polyquaternium-10, Polyquaternium-7, Polyquaternium-11, Guar hydroxypropyltrimonium chloride. Examples of silicones include dimethicone, amodimethicone, cyclopentasiloxane, cyclomethicone, dimethicone copolyols, dimethiconol

Viscosity modifiers

Many polymers are very useful in shampoos and conditioning products because they help to thicken and maintain the viscosity of the product, which gives the desired product consistency for the consumer. It is much easier to apply a shampoo or conditioner to one’s hair if it doesn’t escape from between your fingers when poured from the bottle into your hands. Some of these polymers are also used as emulsion stabilizers, as they help to maintain the oil-in-water formulation that is most typical of hair products.

Examples include:

Hydroxyethylcellulose, hydroxypropylmethylcellulose, carboxymethyl hydroxyethylcellulose, harboxymethyl hydroxypropyl guar and carbomer (poly acrylic acid, acrylates/C10-130 alkyl acrylate crosspolymer).

PEG-modified materials

PEG is polyethylene glycol, a water-soluble polymer that is fairly easily chemically reacted with a variety of other molecules. The number associated with the PEG in the INCI nomenclature is indicative of the number of PEG repeat units present. The higher the number is, the greater the water solubility of the modified molecule. These modified molecules can be used as emulsifiers, viscosity modifiers, surfactants, and humectants.Examples include PEG-150 distearate, PEG-100castor oil, PEG-100 lanoli and PEG-10 sorbitan laurate.

Film-formers

Polymers are often the source of “hold” in styling products such as hair gels and hairsprays. These polymers deposit onto the surface of the hair and cause hairs to be attracted to one another through capillary forces. The polymers then dry to form clear films that are strong and hold the hairs together until the film is either removed via washing or the film is broken due to mechanical forces on the hair (combing).

Examples include:


PVP (poly N-vinyl-2-pyrrolidone) – excellent film-former, substantive to hair, forms clear films, completely water soluble, but it absorbs water which in humid weather can make it sticky or tacky to the touch and can cause frizz and a dull appearance to the hair. In dry weather, it can become brittle and flakey.


PVA (polyvinyl acetate) – resists absorption of water in high humidity which leads to better hold in damp weather conditions, more flexible in dry weather so it doesn’t flake, not as substantive to hair.

PVP/VA copolymer – This polymer provides the best of both worlds. It is a copolymer of PVP and PVA and is used to get around a lot of the limitations of the two polymers exhibit when used individually.

Summary

As you can see, polymers are everywhere in our world, including in our hair care products. Many of the qualities we most desire in our products are given to us by polymers. They can be specifically tailored to meet the required need, and thus will most likely continue to be used and continue to provide us with the benefits we have come to expect.

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