CurlChemist

One of the many conundrums in the world of curly hair is that some people experience a relaxation of their curls as their hair gains length, while others experience the converse: their curl increases with the length of their hair.

The former trend makes sense without having to give it much thought. Longer hair has more weight and is pulled down by gravity, which lengthens and loosens the curl. However, the latter phenomenon seems counterintuitive.

This behavior can be so perplexing, causing curls to disappear with a haircut or to suddenly begin developing as someone grows their hair out for perhaps the first time. While this seeming contradiction may be baffling and even frustrating, it is possible to understand what is going on if one looks at what causes hair to curl and some mathematic principles that can be used to describe curly hair.

Morphology of Hair

Human hair is a marvelously complex biomaterial, comprised of many nanoscale substructures woven together into intricate patterns, both beautiful and functional. The building block of hair is the protein keratin, which is made up of long chains of amino acids. The amino acids in the keratin strands have very specific bond geometries that give the fiber an α-helical conformation. Individual keratin fibers bundle together with other keratin fibers to form aggregates called microfibrils. Clusters of microfibrils bundle together into macrofibrillar structures which occupy the central cortex of the hair. Fatty acids and keratin-based cuticles encapsulate the entire strand.

Human hair keratin is made up of 14 percent sulfur-containing amino acids (cysteine and cystine). It is from these amino acids that many of the properties of hair are developed, particularly curl. When two strands of keratin are adjacent to one another, the –SH bonds for nearby cystine groups can be oxidized to form a disulfide (S-S) bond between the two strands. This is a chemical crosslink that ties the adjacent keratin strands together. A high proportion of disulfide bonds twist the hair strand into a helical pattern. Adjacent hair strands tend to assume the same pattern, and then cluster together into multi-helical structures that form curls. In this manner, the nanoscopic structure is repeated at the macroscopic level. Nature loves patterns.

The permanent wave process exploits this by breaking disulfide bonds and then reforming them (and forming new ones) with hair locked into the desired helical shape.  

There are a number of factors that contribute to degree of curliness.  These include, but are not limited to:

1. Shape of the hair follicle – Teardrop-shaped, cylindrical and oval follicles all produce hair with differing degrees of curl.
2. Angle of emergence of hair from scalp – Super curly hair has been found to emerge from the scalp at a different angle than straight hair.
3. Cross-sectional geometry of hair strand – Completely cylindrical hair strands are straight, while oval strands have more wavy characteristics. Flat, ribbon-like strands result in extremely kinky curly hair.
4. Quantity of disulfide bonds – A higher concentration of disulfide bonds results in a more pronounced helical pattern.
5. Prevalent morphology of cortex cells – The aggregation pattern of the macrofibrillar structures in the cortex affects the degree of curliness.
6. Presence of other genes or proteins – Several different research groups are exploring the presence of a protein that seems responsible for curl formation.

Helical Structures

We have established that the helix structure repeats throughout the hair from its most basic molecular building blocks into the bulk hair pattern. But what exactly is a helix? You may recall the spiral staircase geometry of the DNA-double helix strand from high school biology. A helix is a ribbon-like coil that occupies three-dimensions and is governed by specific trigonometric equations used to describe the length of revolutions and the pitch angle.

X (t) = r cos t

Y(t) = r sin t

Z = ct

Where t = [0,2π], c = constant, r = radius, and 2πc = vertical separation of the loops.

This three-dimensional mathematics can become a bit tricky to visualize, so it can be easier to eliminate the third dimension (z) and think in terms of two-dimensional sine waves. Sine waves can be used to model many different types of oscillating cycles that occur throughout nature, such as sound waves, visible light waves, and radio waves. In trigonometry, we call the length of time or distance it takes to complete one full cycle the period.

If one were to examine a spiral hair curl, it would be possible to see that one full curl revolution would be equal to one complete cycle or sine wave. The distance required to complete one full cycle varies for everyone. Very kinky curly hair would complete more revolutions per the same distance than hair that is less curly. Think of it as higher frequency curl pattern.

Take an example of three different people, with three different degrees of curl, all having hair nine inches in length.

Person A: Her hair completes one full spiral in one inch. In nine inches, it complete nine full revolutions and appears to very kinky curly. If she were to grow it out longer, the weight would eventually stretch the curls out a bit, so that her curl pattern would relax. She would be said to have Type 4 hair.

Person B: Her hair completes one one full spiral every three inches. In nine inches, her hair completes three full revolutions and appears to be mildly curly. If she were to cut it short, it would appear wavy or even straight, but grown longer, it would develop into well-defined spiral curls. She would probably be said to have Botticelli or Type 3 hair.

Person C: Her hair completes one full revolution in six inches. In nine inches of length, her hair only completes one-and-a-half revolutions and appears merely wavy. If she were to trim her hair to be six inches or less in length, it would appear straight. If she were to allow it to grow out to be very long (eighteen inches or more), she would begin to see a pronounced curl pattern emerge. She might be said to have Type 2 or Type 3 hair, or even straight hair, depending upon its length.

Final Thoughts

Human hair is such an intricate structure, and it varies so much from person to person. The helical structure present in our very DNA makes itself apparent on a nano-level in the keratin strands that make up the foundation of our hair and is repeated at higher and higher levels until it is expressed in the gorgeous spiraling curls of our “kinky-haired” sisters and brothers.

Most of us with curly hair find ourselves with a mixture of all sorts of curl types on our heads, and we spend a lot of time and effort attempting to enhance, define and control them. Those with hair that takes longer lengths to really develop and show the curl patterns would do well to keep that in mind when cutting out hair. Lack of caution can lead to a disappearance of those precious curls. Remember the mathematics.

In order to get the best results in your curl pattern, you can figure out what your length for one revolution is and keep it in mind when growing or cutting your hair.

In the curl community, lots of energy is invested into contemplating and analyzing the performance of hair care products. However, most consumers probably give little conscious thought to the appearance of their favorite products, although they are definitely influenced by this seemingly irrelevant property.

Not surprisingly, product formulators spend a lot of time optimizing products to make them visually appealing to a consumer. The incorporation of pearlizing agents, opacifiers, and artificial colors are all methods used to create products that give the visual impression of luxury.

Why do products need cosmetic enhancement?

Shampoos and conditioners are mixtures known as oil-in-water emulsions. The major component is water, with various types of surfactants, emulsifiers, and oil-phase components dispersed into the aqueous phase via formation of micelles. Oftentimes, the concentration of non-water soluble ingredients is sufficiently high to render the micelles larger than the wavelength of visible light. This causes light to be scattered, creating a cloudy solution. Hazy solutions are not regarded as appealing by most consumers, as they can give the perception of not being clean or pure.

Another potentially unpleasant phenomenon is that certain useful ingredients can impart a yellow or amber hue to the finished product. This subtle discoloration can make consumers uneasy, as that color is often associated with spoilage or rancidity. A bright white or creamy ivory colored product is generally rated as cleaner and more attractive.

It is the goal of formulating chemists to create a product that appeals to all of the senses of their consumers, so they take definite measures to make their products more visually attractive. Happily, the solutions developed are not only capable of masking cloudiness or yellowing, but can also yield a highly pleasing final product.

How do they do it?

There are several different approaches a formulator can take to improve the appearance of her product. One technique popular in the 1970′s was to cover any yellow or amber hues by using enough blue and/or green dye to create a blue or green product. These were not very natural-looking and were often fairly runny in consistency.

Current approaches seem to favor the use of only enough color to counteract the yellow and create a white or ivory product. Another trend for brands that market products as “natural” is to use a mixture of red, blue, and yellow dyes to create a brownish products that remind the consumer of clay or earth.

An additional method to overcome hazy solutions is to incorporate opacifiers into the formula. These materials create a homogeneous, solidly opaque appearance to the shampoo or conditioner. Dow markets a line of polymers intended for this use, and the marketing materials say they create a “rich, creamy look, with a dense uniform opacity.” The use of polymers also helps to increase the viscosity of the system, which consumers also interpret as thick and luxurious.

Dow has several different polymers available for this purpose, each specially synthesized to be compatible with different common systems. Ethalkonium chloride acrylate/HEMA/styrene copolymer is cationically charged and is compatible with most cationic conditioning products. They also have an anionic opacifier for use in shampoos, soaps, liquid hand soap, and body washes, all of which traditionally rely upon anionic surfactants for cleansing purposes.

A non-ionic version is sufficiently flexible to be incorporated into a variety of types of formulations, and is especially useful in silicone-containing formulae. These types of materials make bright white shampoos and conditioners that are creamy and thick.

Pretty in Pearls

Perhaps a favorite method for overcoming problems with cloudiness and yellow hue in personal care products is to use pearlizing agents. These materials not only act as opacifiers, but also impart an iridescent luster to a product that is considered to be highly attractive to consumers.

This look can be achieved by using naturally-occurring minerals such as marine aragonite powder (real pearl) or titanium oxide-coated mica particles, but more often is achieved via use of synthetic fatty acid ether esters. The synthetic esters most often used are ethylene glycol distearate (EGDS) and ethylene glycol monostearate (EGMS). Others are PEG-8 dioleate, myristyl myristate, ethylene glycol dipalmitate, and other esters. These materials crystallize in solution into flat platelets that have a very high refractive index. Optical interference from these platelets creates a pearlescent appearance in products containing these materials.

One drawback to using materials such as EGDS is that the somewhat tricky process for adding them during manufacturing.  Temperatures must be elevated above the melting point of the EGDS. In order to obtain the highest quality pearlescence, the crystallization process must be carefully controlled, which means that the mixing rate and forces must be carefully monitored, and the rate of cooling must also be very controlled.  Crystals of just the right size,  and of the smoothest, most regular shape provide the best, most lustrous appearance.  This can be costly and troublesome.

Chemical suppliers are vying for market share for these types of relatively simple-to-make ingredients. One way they seek to differentiate themselves is to provide blends that contain these pearlizing agents already dispersed into surfactant-containing mixtures. These blends have varying features to recommend them, depending upon the package, but typically, the most valuable feature is that they can be processed at cold temperatures and require much less oversight of the manufacturing process to develop the optimal crystalline structures. They are also often times more stable in typical storage conditions. Ease of processing reduces costs for the manufacturer, which translates into these pearlized products being more affordable for the consumer.

These materials can have some slight humectant or moisturizing properties for hair or skin. Generally though, they are not going to significantly impact the performance properties of your favorite shampoo or conditioner. Most opacifiers and pearlizers have sufficient polar or amphiphilic character as to be easily removed from hair (if they remain on the hair in the first place) via a conditioner wash or mild shampoo cleanse.

Final Thoughts

So the next time you pick up a product, in addition to considering its performance and fragrance, take a moment to ponder and appreciate its appearance as well. A bunch of scientists somewhere put a lot of time and thought into making it attractive to you. It is an important part of the whole package.

A discussion took place recently on the CurlTalk forums about how difficult it can be to find reliable, accurate scientific information regarding hair product ingredients. The uncontrolled nature of the internet means that anyone can post a video, blog, or advertisement, claiming to be an expert and dispense information and advice. Quite often, it is evident that there is a bias or undisclosed motive behind the information being presented, which certainly fosters distrust.

Perhaps most frustrating to some of the participants in the discussion was how often supposedly credible experts disagree with one another on key points. Some even expressed confusion as to whether there is a specific area of scientific study directed at understanding hair and how its properties are affected by products, and if so, it was assumed it must be a rather new area of study.

So why does this seem to be so challenging? Is it possible to access solid and unbiased information on hair and the products we use on it?

It is Definitely Science

The vast amount of information made readily available to the public on the internet in the past decade has made it possible for consumers to educate themselves about the products they use to a far greater extent than ever before. However, the fact that the information is new to a more general audience should by no means be taken to mean that the information or the field itself is a new one. The study and development of hair and skin care products is generally referred to as cosmetics science or cosmetics chemistry. Unfortunately, that name can trivialize the field due to the perception that cosmetics are a superficial or less important area of research than other subjects deemed more critical. Certainly, the term “cosmetics science” is not particularly revealing of the scope of the scientific principles involved in developing products that meet the high requirements of the consumers.

Cosmetics science is a multidisciplinary one, relying upon many different areas of scientific expertise. No single person possesses in-depth expertise in all of the areas. Within huge finished goods, manufacturers such as Unilever and Proctor & Gamble and suppliers of raw materials such as National Starch, BASF, and DuPont, there are teams of scientists with different areas of expertise, working to develop and optimize hair product ingredients and final products.

• Microbiologists: These scientists typically possess either a master’s or doctorate in their field, and they study growth of microbes and fungi in products, and develop and optimize preservation packages.
• Polymer Chemists: Typically possessing advanced degrees in organic or physical chemistry or in polymer science, these scientists develop or use new polymeric materials to achieve specialized effects in products.
• Physical & Analytical Chemists and Materials Characterization Experts: These scientists come from a wide background and perform tests ranging from the simple to the highly sophisticated on raw materials (ingredients) and finished goods.
• Colloid & Surface Chemists/Scientists: These scientists have advanced degrees in organic or physical chemistry and study solutions of oil and water, and find ways to better stabilize or optimize them, or find new ways to  capitalize on their properties.
• Formulation Chemists: These scientists who develop the finished goods formulas can come from a broad range of backgrounds, such as chemistry, biology, and pharmacy.
• Biochemists: Graduate studies in various areas of biochemistry prepare these scientists for study of proteins, skin, hair, and plant-based materials.
• Chemical & Production Engineers: These engineers work with the formulation chemists to help the product make the transition from a small lab-scale formula to a large-scale manufacturing process.
• Cosmetologists: Many of the larger companies have in-house hair salons, where they can do focus groups and testing of new products, to obtain and quantify customer responses.

Xanthan gum is found in many products, including food items, cosmetics and personal care products. It also appears in many shampoos, conditioners and styling agents. Its current popularity can in part be attributed to its plant-based origins and biodegradability. Home-based kitchen chemists who formulate their own products have found it to be a useful and easy-to-use additive for hair gels and conditioners.

What exactly is this material, though? Its name does not reveal much information regarding its chemical nature or its purpose in a product.

Xanthan Gum’s Chemical Structure

Xanthan gum is a naturally derived polymeric carbohydrate (polysaccharide) with a very high molecular weight (in the millions of grams per mole). It is obtained via a fermentation process utilizing the bacterium Xanthomonas campestris, which can be obtained from a variety of plant-based sources.

The polymer backbone is comprised of repeating units of a simple sugar molecule (beta – (1,4) D-glucose), and the side chains pendant to the backbone are trisaccharides, made up of alpha-D-mannose, beta-D-glucoronic acid, and beta-D-mannose paired with a pyruvate group. The side chains possess an anionic (negative) charge, and they make up the bulk of the weight of the polymer, and thus contribute the majority of the properties for which Xanthan gum is prized.

Xanthan Gum’s Physical Properties

Xanthan gum is readily soluble in either hot or cold water. It is generally unaffected by pH, is very tolerant of electrolytes, and is stable over a wide range of temperatures. These properties make it extremely easy to work with both in formulation and production.

Xanthan gum is most often used for its unique rheological (affecting the flow of the liquid) properties. In both neutral and charged solutions, it imparts higher viscosity to the formula, making it thicker and more resistant to flow. In a neutral solution, the polymer molecules are in the random coil state, and thickening is achieved primarily via chain entanglements between the very long polymers. Imagine a mass of spaghetti noodles all piled together in a bowl and how they all become intertwined with one another.

In solutions containing electrolytes, the polymer molecules collapse and form somewhat rigid helical rods that can pack together and form gel networks via hydrogen bonding. Polymers that form gels when mixed with water like this are called hydrocolloids. These gels are stable over a wide range of temperatures. Also, since the polymers are completely soluble in the aqueous solution, the subsequent gels formed are very clear, which is a highly desirable property in the styling product market.

Hydrocolloid gels made with xanthan gum are pseudoplastic materials, meaning that the viscosity of these solutions undergoes shear thinning (decreases) when a shear force is applied. This makes it easier for the fluid to move or flow when it is shaken, stirred, or squeezed. What happens is that the forces break down the gel network so that the individual polymer molecules can slide past one another.

This is a great advantage both for processing the materials as well as for application as a finished good. Shear thinning reduces the effort required to squeeze or pump gel or lotion out of a bottle or toothpaste from a tube, which renders it easily applied to hair, skin, or a toothbrush. Once the shear force is removed, the gel network re-forms and the viscosity builds up again. This makes xanthan gum an excellent emulsion stabilizer also.

Recently, there have been a number of articles and discussions comparing and contrasting silicate and silicone hair care products. The similar sounding names have led to some understandable confusion regarding the nature and purpose of these ingredients in shampoos and conditioners. Both are common ingredients found in a variety of products such as skin cleansers, shampoos, creams, masques, and hair conditioners.

Many curly-haired consumers avoid silicones or attempt to minimize or restrict their use in their hair care routine. However, the use of silicate-containing products is occasionally advocated based on the premise that they are “natural alternatives” to synthetic silicones. Unfortunately, this information is not entirely accurate and stems from a misunderstanding of the chemical nature and structure of these two very different types of materials.

A closer examination of the chemical and physical properties of each category should be useful for anyone who is curious about the molecular nature of these ingredients and what function they perform when included in hair care products.

Silicones

The Bane of the Curly World

Silicone hair products have been discussed extensively on this website and others, so this will be a quick review rather than an exhaustive treatise. They are a diverse family of synthetic inorganic polymers based upon polydimethylsiloxane that can be prepared and modified in numerous ways in order to produce materials suitable for a wide range of applications.

Silicones used in hair care products are typically long, flexible molecules with a backbone comprised of thousands of repeat units of some variation of –(O-Si-O)- linkages with differing organic (carbon-containing) pendant groups attached to the central silicone atom. These are typically liquid at room temperature and are oily in their consistency. They are most often insoluble in water, but are sometimes modified with ethylene glycol groups or other atoms to render them water-soluble.

The physical properties of silicones cause them to adsorb onto the surface of hair and to spread out, forming a smooth film, which increases slip along and between hair strands and decreases combing forces. This renders them superior conditioner agents and detanglers. Additionally, they provide thermal protection, which reduces structural damage incurred from the use of heated styling tools. They have also been found to increase the longevity of color in dyed hair.

Silicone polymers have a high refractive index, which allows them to impart an extraordinary level of gloss to the hair, which gives the appearance of shiny, glamorous tresses. Clearly, despite their reputation in the curly community, silicone polymers provide many direct benefits to hair when used in shampoos, conditioners and styling products.

Common Silicones in Hair Products:

• Dimethicone
• Cyclomethicone
• Dimethiconol
• PEG-modified dimethicone
• Amodimethicone
• Various copolymers

Silicates

Not a Silicone Replacement

Silicates used in hair and skin care products are inorganic minerals called clays, which are mined from the earth. Similar to silicones, these minerals are comprised of silicon and oxygen. However, the similarity ends there. Unlike silicones, these are not long chains of repeat units, but are rather small clusters of ionically-charged, crystalline platelets with various metal ions associated with them.

Silicates are extremely hygroscopic, meaning not only are they water soluble, but they will absorb large quantities of water. Due to this property, as well as their plate-like structure, these materials are used in shampoos and conditioners as viscosity modifiers (thickeners). They are also effective as exfoliating agents, humectants and slip agents. They act as emulsion stabilizers and help prevent flocculation of ingredients. They have been found to have some beneficial properties for hair because they can help remove impurities and improve the health of the scalp.

However, silicates do not provide significant conditioning, detangling, thermal or color protection, nor do they impart gloss to hair. Their primary benefit is to the physical properties (viscosity and shelf stability) of the formula in which they are included. They are not typically part of a formula for the same reasons as silicones at all. They are not silicone substitutes.

Common Silicates in Hair Products:

• Aluminum magnesium trisilicate
• Zirconium silicate
• Calcium silicate
• Sodium Silicate
• Bentonite Clay, sodium or calcium bentonite
• Montmorillonite clay

The Bottom Line

• Both silicones and silicates have significant, yet extremely different benefits, when used in a formulation.
• A person who chooses to avoid silicone hair products due to concerns about build up on the hair need not avoid silicates.
• However, one should be aware that silicate clays do not act as substitutes for silicones, and excellent conditioning products need to still be used regularly.

Accumulation of mineral scale on surfaces due to hard water build up is an unfortunately common and truly aggravating problem. Most people have experienced the joys of living with hard water: cloudy, spotty dishes coming out of the dishwasher, diminished performance of coffeemakers, clogged or broken pipes and washing machines with an unpleasant odor that don’t work properly, turning clothes and towels dingy grey or a rust-tinged color.

Hair is susceptible to this menace as well, becoming dull, limp, or frizzy and more prone to tangles and hair breakage due to accumulation of minerals causing hair build up. Certain strong shampoos, such as clarifying or chelating ones, are marketed as solutions to some of this, but are there any options for those avoiding sulfate-based surfactants? As always, the answer to that question lies in the chemistry and materials science of the system.

Why Hard Water Creates Hair Build Up

If you have hard water, removing hair build up should be part of your hair care routine.

Hard water contains significant quantities of dissolved minerals, such as iron, calcium, magnesium, and silicon. These metals can react with substances in soaps and shampoos and reduce the effectiveness of those products’ cleansing properties, making it necessary to use more of the cleanser. But, even more disturbing, is that fact that the reaction products precipitate out of the solution and deposit onto the surface of your hair, where they bind with the negatively charged surface. This is what is typically referred to as mineral scale, which conjures up a bit of a mental image, if one considers it. Picture hard fish scales covering your hair, creating a rough surface that prevents moisture from penetrating the hair shaft, and you won’t be too far removed from the reality.

These deposits also attract and trap organic matter such as grease and dirt. This leads to hair that becomes increasingly difficult to deal with. It becomes dull instead of glossy, loses curl retention capability, is more prone to formation of snarls and tangles and is more easily damaged. It can even lead to the development of an unpleasant odor to the hair, particularly in dreadlocks.

Clearly, this kind of hair build up is not a trivial issue and should be addressed as a normal part of a person’s hair care routine.

How to Prevent Hair Build Up

The absolute best method for dealing with hard water is to prevent hair build up in the first place. One can do this by utilizing a good water filter that removes the unwanted metal ions from the water. Another technique is to use a chelating shampoo regularly, which has molecules in it such as EDTA, or acetic or citric acid. These acids bind with the metals in the water as you are washing your hair and are then rinsed away instead of depositing onto the surface of your hair. These shampoos can be harsh, though, and should always be followed up with a good conditioner, but even then, they may be damaging to curly hair if used too often.

Vinegar rinses can possibly help loosen mineral scale so it can be rinsed, and it definitely helps dissolve some of the trapped organic matter that can be lurking in the residue. Clarifying shampoos can also help remove hair build up. It is not clear whether they actually remove mineral scale from hair, but they definitely can provide deep cleaning of any other matter adhering to the surface because of the mineral scale.

Chelating shampoos may be able to dissolve the mineral scale and help remove it from the hair. The Beauty Brains, a site run by cosmetic chemist/consultant Perry Romanowski, states their skepticism as to whether this works at all, which makes me yearn, yet again, for a lab with some really expensive equipment so I could run some studies, both to satisfy my own curiosity and so I could also give you all a definitive answer.

Gentle shampoos with surfactants designed to provide mild cleansing are undoubtedly capable of removing organic material and hair build up. This includes surfactants such as sodium cocoyl isethionate and coco betaine. However, it seems unlikely that these would have the ability to remove mineral scale by themselves. Fortunately, there are definitely some shampoos that contain mild surfactants, no added conditioning agents, and acids that are thought to aid in removal of hard water hair build up.

Final Thoughts

Since it is so evident that curly hair performs absolutely at its best when it has both a clean surface and a well-moisturized cortex, it seems imperative that you take some sort of measure to prevent or remove hair build up caused by hard water. The installation of a water softener or filter seems to be the best and most proactive solution. However, there are other alternatives, such as rinsing with vinegar and using chelating shampoos. It is of utmost importance that an excellent conditioner be used whenever one uses strong products like this on the hair, so don’t skimp on that step.

The science of hair care has been a lively area of research and development for the past 50 years or more. Tremendous strides were made in the past two decades alone, thanks to advances in polymer and colloid chemistry. These advances were found in both the area of designing and producing extremely complex polymeric molecules and also in the area of understanding the mechanisms by which these molecules provide benefit. The incorporation of highly sophisticated polymers and polymer combinations into formulations has yielded curly hair products capable of truly protecting and enhancing hair, and efforts to optimize existing polymers and to synthesize new types are ongoing.

Silicones

Many currently available moisturizing curly hair products rely heavily upon the use of cationic polymers and silicone-based polymers as conditioning agents. Silicone polymers provide excellent smoothing of the cuticle, impart shine, protect hair from thermal damage, increase longevity of hair color and yield positive tactile feel to hair. Cationic polymers can work together with silicones to enhance their performance in conditioning shampoos. They can also work alone to provide excellent conditioning benefits, including superior combing force reduction.

However, these ingredients and the products that contain them have recently waned in popularity with consumers, primarily due to concerns about buildup of those substances on hair. This trend has not gone unnoticed in an extremely market-responsive industry, and has, in fact, been a huge driving force behind research and development efforts. These projects have been ongoing, both at raw materials suppliers and finished good manufacturers, with the objective to develop and produce replacement polymers and silicone-free formulas.

One such project recently came to fruition when Dow Personal Care, a subsidiary of Dow Chemical, released its new conditioning platform, EcoSmooth Polymer Technologies.

Their product literature states that the platform is comprised of two types of polymers: EcoSmooth Silk and EcoSmooth Satin, which they claim will “reinvent conditioning.” An examination of these polymers and how they compare to more commonly utilized polymeric conditioning agents may provide curlies with insight to help them decide whether or not to give these materials a try.

EcoSmooth Silk

EcoSmooth Silk is a polyolefin water insoluble copolymer emulsified using a proprietary acrylic-based polymer dispersant with the INCI name: ethylene/octene copolymer and ethylene/sodium acrylate copolymer. This polymer is marketed as a replacement for silicone.

Marketing and technical literature published by Dow Personal Care describes EcoSmooth Silk as “a non-cationic technology that matches silicone in wet and dry combing and minimizes hair breakage.”

Although this polymer is a hydrophobic one (i.e. not water soluble), Dow reports that they did not observe evidence of appreciable buildup after repeated use. The method they used to make this assertion was based upon volume of the hair after repeat application. With silicones, which do build up over time, hair volume is found to diminish. Hair treated with the EcoSmooth polymer was found to have greater volume after multiple applications than that treated with silicones.

No actual chemical analysis or surface analysis of the hair was reported or described to substantiate this claim, although it may exist. This polymer should be removable using a mild shampoo, but shampoo-free users may wish to proceed with caution.

EcoSmooth Satin

EcoSmooth Satin is a non-cationic conditioning polymer with the INCI name: Ethylene/Sodium Acrylate Copolymer. It can be used to replace cationic polymers such as polyquaternium-7 and guar.

Dow claims that it provides equivalent sensory and foaming performance to those two polymers and that it provides superior performance on damaged European hair in particular. This means that the tactile feel is better to the consumer both during and after use.

When compared to cationic guar applied to damaged hair, EcoSmooth Satin was found to demonstrate a superior ability to reduce wet combing forces, making it easier to detangle hair and to significantly reduce the percent breakage of hair.

Satin is a water-soluble anionic polymer in solution that deposits onto the surface of the hair via a dilution deposition mechanism, where it binds to hair via hydrophobic interactions. Cationic polymers bind electrostatically to the surface of negatively charged hair via a charge-charge interaction. So, while both types of polymers are water soluble, Satin should be more easily removed from the surface of hair due to weaker interactions between the hair and the polymer.

For this reason, it seems reasonable to expect a buildup free experience when using curly hair products containing this polymer, presuming other ingredients in the formula are not prone to build up themselves.

Wrap-up

It is truly exciting to observe the sophisticated application of polymer science to the development and optimization of hair conditioning products. Silicones and cationic polymers have provided formulators with seemingly endless formulas that have truly stellar performance on hair.

Yet, there are many more possibilities, as Dow has clearly demonstrated with the launch of EcoSmooth Polymer Technologies. These polymers appear to be promising as conditioners used in curly hair products, as they seem to be less prone to buildup and also have demonstrated an ability to reduce breakage.

It will be interesting to see how these materials work in commercially available products, and also to see what other polymers will emerge onto the scene in the future.

Illustration of oil droplets suspended in water (emulsion)

Illustration of a micelle

Depiction of a sterically stabilized emulsion

Recently, an insightful reader asked whether a certain styling product advertised as “water-soluble” could possibly be so. The specific reason for the inquiry was the presence of petrolatum and mineral oil near the top of the ingredients list. Of course, my reflexive response to this question is “no.” Petrolatum and mineral oil are both decidedly hydrophobic materials, and they are not, nor will they ever be, water-soluble. However, this product is definitely described in the marketing material as being water-soluble, so it seemed worthwhile to give this a closer look and see what answers may be found in the chemistry of the formulation.

The product in question is Curlisto’s Unruly Paste, recommended for use on dry hair to provide curl definition, shine, and to tame frizz. It is described on their website as being non-sticky, non-oily, and “water-soluble.”

It is possible to glean a good bit of useful information about Unruly Paste by analyzing the ingredients list. Unlike many similar types of products, this is a water-based styling crème. It contains humectants (propylene glycol), a water soluble fixative polymer (VP/VA copolymer), a significant percentage of higher molecular weight oils/waxes (petrolatum, mineral oil, and ozokerite – a mineral wax mined from the earth), a non-water soluble silicone for shine and smoothing, and a large quantity of emulsifying agents.

Micelles are aggregates of surfactant molecules in water, comprised of an exterior shell of the hydrophilic portion of the surfactant and a hydrophobic center containing the non-polar segment of the surfactant. In this product, the surfactants form micelles that contain the mineral oil, petrolatum, and/or ozokerite in their core.

The nonionic emulsifying agents prevent coagulation and phase separation of the waxes by a mechanism known as steric stabilization. This is where the hydrophilic portions of the surfactant molecule extend out into the aqueous solution and form a bit of a tangle around the micellar aggregate. This tangle physically prevents micelles from coming together and joining to form bigger micelles, a phenomenon that would eventually destabilize the system and result in phase separation.

Technically, the non-polar waxes are solubilized or dispersed into the water using these emulsifying agents and are water soluble while in these aggregate forms. To reiterate, they are only soluble by nature of their containment within the interior of the micelles formed by the surfactants. (You may recall that we have had similar discussions about amodimethicone, as used in certain shampoos and conditioners.) These types of mixtures are called emulsions, because they are not solutions by proper definition.

Once the product is applied to the hair, the micellar structures are disrupted, the waxes are deposited onto the surface of the hair, and the water from the product evaporates into the air. Since this is a leave-in product, the surfactants remain on the surface of the hair even after the water evaporates, but they no longer serve much purpose except to perhaps attract water molecules to the hair from the environment.

The question is when hair that has been treated with this crème is immersed in water, will the emulsifying agents somehow re-form the micellar structures and re-absorb the waxes into their cores, allowing them to be rinsed away? It is my opinion that this scenario is highly unlikely, as the original process of preparing the product relies heavily upon proper order of addition of ingredients, judicious mixing and agitation, as well as the application of heat in order to form these types of structures in the first place.

However, it is possible that if one were to use a very mild shampoo or even a light conditioning product and gently agitated the hair, that the residual emulsifying agents on the hair might be able to aid in removal of the waxes from the surface of the hair. Generally, one would need to use quite potent shampoos to remove petrolatum and mineral oil from hair, and it would probably be necessary to rinse and repeat.

Final thoughts

Thus, it would seem possible that this method could alleviate some of the accumulation that inevitably occurs from use of typical products that rely upon these types of waxy ingredients. “Water-soluble,” though, seems to be a bit of a marketing stretch.

One of the primary indicators of the health of your hair is its elasticity. Healthy hair has a high level of elasticity, which gives it body, bounce and curl formation. Elasticity makes it possible to style hair and also is responsible for curl retention. But what exactly does the term elasticity mean? We know it has to do with the stretchiness of our hair, and we know it is a desirable property, but it may not be entirely clear what it is.

Also, what contributes to elasticity of hair, and how can we maintain or improve the quality in our own locks? These are important questions, and as always, much insight can be gleaned by an examination of the fundamental principles as well as the molecular structures that make up the hair.

What Does Elasticity Mean?

Elasticity is a term used to describe how a material responds to the application and removal of a specific type of mechanical load (pulling and/or bending). When a stress (force per unit area) is applied to a material, it stretches a certain amount beyond is original length. This deformation is dependent upon the stiffness or rigidity of the material. The ratio of applied stress to the amount of deformation/elongation that occurs is called the elastic (or Young’s) modulus.

Rigid materials, such as iron, stretch very little with an applied force, while other materials, such as synthetic rubber, can stretch many times their original length without breaking. Dry hair can stretch to approximately 1.2 – 1.3 times its original length and still return to its dimensions, while wet hair is less rigid than dry hair and can stretch up to 1.5 times its length. Curly hair can stretch even than straight hair, as it is highly coiled in its relaxed state.

In the cosmetics and hair care industry, a continual stream of new products are introduced into the market. Most seem to be variations of whatever happens to be the current popular theme. On occasion though, new products emerge onto the scene bearing remarkable claims that demand closer examination.

One such recent case is the Nexxus Pro-Mend system, which the manufacturers assert can nourish hair and actually heal split ends. Who wouldn’t be intrigued by promises that the product could repair up to 92% of split ends in the first use? It seemed a sufficiently brazen claim to warrant some scientific detective work to determine if the claims are credible, and if so, what the chemical basis is for the reported miracle cure for split ends.

Too Good to Be True?

The initial response many may have when hearing such a claim is that it is preposterous. We have all been taught that hair is a “dead” protein, and that topical treatments such as hair products are incapable of providing anything other than cosmetic, superficial, and temporary benefit. However, our understanding of and facility with protein and polymer chemistry has been continually advancing in unexpected and oftentimes brilliant ways. For this reason, I am willing to temporarily set aside my skepticism and entertain the notion that maybe someone has finally found a way to repair split ends without a pair of scissors.

There is a general procedure one can follow to gain fundamental insight into the technology behind a new product. The first step to understanding is to examine the ingredient list and look for anything new or unusual combinations of materials. Next, it is helpful to review the company’s marketing material and instructions for use of the product. Finally, one can gain a tremendous amount of valuable information by scouring the relevant technical literature and patents (even those of competitors or for products used for completely different applications).

Analysis of the Ingredients

Nexxus Pro-Mend Leave-In Treatment Cr̀eme Ingredients

Water, Phenyltrimethicone, Dimethicone, Stearamidopropyl Dimethylamine, Polyquaternium 37, Polyquaternium 28, Cetyl Alcohol, Glycerin, Cyclopentasiloxane, Aspartic Acid, Propylene Glycol, Dicaprylate/Dicaprate, Fragrance (Parfum), PPG 1 Trideceth 6, Glyceryl Stearate, PVM/MA Copolymer, Dimethiconol, DMDM Hydantoin, Disodium EDTA, Sodium Hydroxide, Hexylcinnamal, Butylphenyl Methylpropional, Limonene, Coumarin, Linalool, Alpha Isomethyl Ionone, Cocos Nucifera Oil (Coconut), Keratin Amino Acid,Jasminum Officinale Flower Extract (Jasmine)

I was slightly taken aback by the ingredients for the products in the Pro-Mend line, which were not exactly what I expected to see in a novel intense conditioning formula. The major components listed are silicones and polyquaternium conditioning agents. The use of cationic polymers (polyquaterniums) is not surprising, as they are selectively attracted to damaged areas of hair (which bear a negative charge). For this reason, they can be particularly useful in smoothing damaged cuticles and managing split ends. However, this is not a novel application of these materials. At first glance, nothing else jumped out as a likely character that would be able to repair split ends.

The first eight ingredients after water are found in many conditioning products, so no surprises there. After that are oils, emulsifiers, humectants, solvents, one fixative, and other common conditioning agents. But again, none of these ingredients are really known for doing anything terribly novel in terms of hair repair. Most are topical film-formers possessing varying ability to smooth, condition and protect the surface of the hair.

So, was that it? Was Pro-Mend merely another iteration in the long line of conditioning products available? Perhaps not. After further contemplation of the formula, I began to think there was more to these products than first meets the eye.

Several ingredients stood out in the list and nagged at my subconscious. Among these were Aspartic Acid, DMDM Hydantoin, Sodium Hydroxide, Hexylcinnamal, Butylphenyl Methylpropional, and Keratin Amino Acids. These ingredients are not uncommon and each has its own typical and often mundane purpose in a product. However, some of these are capable of performing double duty, and the presence of all of these ingredients together led me to have some suspicions as to how this product could possibly do the things they promised it could do. But, I needed more information.