CurlChemist

Cleansing ingredients found in shampoos belong to a category of molecules called surfactants (surface active agents). These materials are comprised of both polar and non-polar segments. The polar segments are water soluble and are referred to as hydrophilic, which means water loving, while the non-polar segments are only very slightly soluble in water due to a lack of sites for favorable interactions with water molecules. The terms hydrophobic (water fearing) and lipophilic (oil loving) are used interchangeably to describe the non-polar portions. Since surfactant molecules possess both lipophilic and hydrophilic qualities, they are referred to as amphiphilic materials.

Frequently, the hydrophilic portion of the surfactant exists on a terminal end of the molecule, and for this reason, is often referred to as the head group. The hydrophobic segment of linear surfactant molecules is typically an alkyl- or aryl-containing chain, and is referred to as the tail group. (Figure 1.) Other types of surfactants, such as bulkier small molecule surfactants with multiple or branched tails, amphiphilic polymers, and biological materials have a more complex molecular architecture that gives them various geometric shapes. Many of these may not possess a distinct head group and tail group, yet they do have definite hydrophilic and hydrophobic segments.

When surfactants are dispersed into water, they cluster together first at the surface of the water, and then at higher concentrations, they cluster together in the bulk of the water and form aggregates known as micelles. In these clusters, the non-polar portions of the molecule all huddle together in the middle of the micelle, while the polar portions form a sort of shield on the outer rim of the micelle, creating a hydration shell and segregating the hydrophobic portions of the surfactant from most of the water. These types of micelles (oil-in-water) can absorb oil into their core and hold it there, while the hydration shell sort of holds the whole thing together.

Most surfactants used for cleansing hair and skin have a negatively charged ion at their head group (example: sulfate) and a positively charged counterion (example: sodium). These are called anionic surfactants. Positively charged (cationic) surfactants are typically used as emulsifiers to facilitate mixing of oils such as silicones and other polymers. Cationic surfactants are also attracted to the negatively charged surfaces of skin and hair, and so they can also be used as mild conditioning agents. Zwitterionic surfactants have both a positive and a negative charge. Some of these, particularly cocamidopropyl betaine, can be quite useful in shampoos and are oftentimes milder than some of the typical anionic surfactants. Nonionic surfactants generally have polar (but not charged) segments with multiple oxygen containing moieties (such as ethylene glycol) and can be quite gentle and effective as cleansing agents.

Representation of a linear surfactant molecule

When determining the relative strength of detergency (oil-stripping ability) of a surfactant, one must consider a variety of things. The size and structure of the tail group is important, as is the size and structure of the polar head group, as well as the size and structure of the counterion (sodium, ammonium, etc.). These are complex properties described by concepts such as self-assembly, critical micelle concentration, packing parameter and the principle of opposing forces.

Essentially, the more compact the molecule and its head group, the more efficiently it can pack into micelles of larger size and capacity. Micelles that are larger can pack more oil into them—thus more efficient at removing oil from the scalp and hair (and other surfaces).

Taking great care of our delicate curly tresses seems to introduce the occasional (okay, frequent) dilemma into our daily routines. One particular problem is that of sopping wet hair and what to do with it. It is possible to protect your hair from thermal damage by avoiding the use of hair dryers, and frizz can be minimized by avoiding the use of regular bath towels as turbans. But, air drying thick, curly hair that is saturated with water and product can literally take hours, which is neither convenient nor stylish. A wet head really doesn’t lend itself to a professional persona either. So, as we endeavor to maintain our professional credibility, avoid catching colds (if you believe that particular old adage), and have the best looking locks we can, sometimes we find ourselves looking for methods or products which might be of assistance to us in reducing the drying time of our hair.

Mechanical Methods

So, what can we do to attempt to speed this process up? Most of us don’t have hours in the morning to wait while our hair dries, but we also frequently prefer the look of freshly washed hair to that of “slept-on” hair. One popular solution has been the use of cotton t-shirts or microfiber towels. These allow one to gently absorb a lot of the water from hair, while reducing friction between hair strands and the cloth. High levels of friction between hair and cloth (such as occurs when using typical terry cloth towels) can lead to formation of tangles, frizz, roughened cuticles, and unpleasant texture. Smoother cloths help minimize this and can speed drying time. It is important to be gentle with your hair, even when using a cotton t-shirt or microfiber cloth, as wet hair is very susceptible to damage.

Simply squeezing water from the hair manually can also enhance drying time. I like to do this very carefully from root to tip in order to not damage the cuticle. However, this method can disrupt curl pattern, so it may be necessary to turn your head upside down and scrunch or plop in order to restore some bounce.

Clipping the hair up in sections at the roots is also an excellent technique for getting hair to dry more quickly. This exposes more surface area of the portion of hair closest to the scalp, which tends to hold the most water, and allows it to escape more quickly and easily. The clipping procedure also helps provide more body and lift at the root by helping hair to dry away from the scalp. It’s a great method!

Products and Ingredients that can Enhance Drying Time

There are definitely products that are formulated with specific ingredients that help to reduce drying time. Many of them come with some sort of downside, but are worth examining.

Not this kind of alcohol

Alcohols

Denatured ethyl alcohol and isopropyl alcohol have been used in products in the past to speed up drying, either of the hair itself or of the product. Some mousses and hair sprays and some gels may still contain these alcohols in them. Low molecular weight alcohols such as these have extremely low vapor pressure and evaporate rapidly from hair, taking water molecules with them. Unfortunately, these ingredients lead to hair that becomes dry and damaged, so they are generally not favored by those of us with curly hair that already tends toward being overly dry.

Cyclomethicones

Cyclic silicones, known as cyclomethicone, cyclopentasiloxane, and cyclotetrasiloxane, are frequently used in light conditioning products and spray-on detanglers for their ability to smooth the surface of the hair and to help speed drying time. These silicones are smaller molecules than their polymeric cousins and are sufficiently volatile that they evaporate fairly rapidly. However, many users have reported unpleasant results from products containing these materials, so one should proceed with caution.

Amine-functional silicones

Silicones such as amodimethicone, which are silicones containing amine groups that give them a positive charge, have been observed to decrease drying time. They have the added benefit of imparting a high level of gloss to hair and smoothing the outer surface of the hair. For this reason, they are a popular choice by formulators for products such as leave-in conditioners and spray-on detanglers. Amodimethicone is also resistant to build-up and fairly easily removed. My favorite detangler uses this ingredient, and I have always been pleased with its performance.

I ran across some patents by Procter and Gamble where they were claiming a newly modified version of an amine-functional silicone polymer with halogenated functionality aided in reducing drying time and also in maintaining style hold in a styling formula. These polymers were touted as being extremely water repellent, resistant to rinsing or washing off, and helping reduce drying time in the future by minimizing water penetration into the hair. This doesn’t seem desirable to me, but there may be some who would like a product such as this, especially if they enjoy products with extreme anti-humectant and anti-frizz properties.

Moroccan Oil and Macadamia Nut Oil

Moroccanoil Treatment and Macadamia Hair Macadamia Natural Oil Deep Repair Masque both advertise wonderful results for hair, both in terms of softness and frizz reduction as well as in reduction of drying time. Both products report between a 40-50% decrease in drying time. I thought this sounded pretty amazing, and was curious to learn the mechanism by which this worked. Unfortunately, when I looked at the formulae for these two products, I found that instead of being natural oils, their ingredient lists were headed by cyclomethicone, dimethicone, and cyclopentasiloxane. I guess we know why they reduce drying time now. This seems to fall under the category of misleading marketing in the “natural” product category.

On the whole, it seems that the various mechanical methods for reducing drying time are safe, effective, and inexpensive. Using several of the methods at a time should speed things up for you (squeezing hair gently, plopping into a microfiber towel or t-shirt, clipping at roots in small sections). Products containing amodimethicone do decrease drying time while maintaining shine and softness and are well-tolerated and even loved by many curly haired consumers. Lightweight conditioners and detanglers containing cyclic silicones perform well for some people, but not for others, so that is something you will have to try for yourself. There doesn’t seem to be much escape from the fact that we simply need to allow more time to get ready than if we were willing to employ some of the more traditional methods of drying one’s hair. I am curious about these ionic hair dryers, but have not looked into them at all. I would love to hear from readers who have experience with them. Talk to me!

I share the frustrations of many of you when it comes to understanding hair products and how hair responds to them. Entirely too often it seems to me that luck or fate have more to do with the mythical condition known as “a good hair day” than anything else. Of course, as a scientist, I know that simply isn’t the case, but it seems impossible (translate: entirely too much effort) for me to analyze all the variables and reliably achieve that elusive state of perfect balance. Why can’t we just formulate products that perform predictably and reliably—this isn’t rocket science, is it? Maybe that is a good question.

The fact is that a huge number of factors influence the behavior and texture of our hair: outside temperature, humidity, dew point, hair texture, hair condition (chemically or thermally treated?), type of products used, order in which products are used, handling of the hair, water quality, etc.. None of this even takes into account the many ingredients in the products we use, and how those ingredients might interact with one another, with your hair, or with the local climate. It is mind boggling and daunting to even the best researchers.

Thus, it seems ironic that in the scientific world, cosmetic and personal care chemistry are often treated with skepticism and have a reputation for being poor science. Despite all that I know of the many principles involved in the development of hair and skin care products, I must confess to having made this accusation myself a time or two, even toward my own projects. My biggest complaint in graduate school was that I just couldn’t get in there and ask those molecules what they were doing!

What’s Bad in Cosmetic Science?

There are some reasons for people having this dim view of the industry. Misleading marketing and outright charlatanism are unfortunately prevalent in the field, with outlandish claims often made without proper data to back them up. Statistics are abused and misrepresented to give the appearance of remarkable results. Preying upon the fears of consumers with heavy-handed ‘safety’ information is also a technique used to convince people to avoid certain products and to purchase theirs.

Other practices in the industry, usually at smaller companies with fewer resources, such as haphazard formulation, inadequate quality control, and insufficient stability testing of new products and raw materials, can erode the trust of consumers and scientists alike. Formulating without a solid grasp of concepts such as emulsion stabilization, viscosity modification, and preservation can result in unpredictable shelf life of a product and also in inconsistent results in application. Extensive testing is necessary to evaluate a product every time the formula is changed, but it is frequently foregone.

Another criticism of the field is that new findings are not always published in peer-reviewed journals, as the data and information are considered proprietary. This helps companies maintain an advantage in an incredibly competitive market, but it can lead to skepticism from anyone who thinks to question their claims. However, there really is excellent and highly scientific work being published by researchers in this area, not only in the trade journals of the field, but also in more academic publications such as “Langmuir,” “Macromolecules,” “The Journal of Physical and Colloid Chemistry,” and others. Patents can also be great sources for information.

What’s Good in the Cosmetic Science?

Innovation and achievement of lasting success in this competitive market requires a strong commitment to fundamental scientific research, with high levels of interdisciplinary expertise and collaboration between experts in various fields. Consumer product companies such as Unilever, Procter & Gamble, Living Proof, Estee Lauder (and many others) devote millions of dollars to doing the highest level of science in order to maintain or grow their market share. Raw material suppliers do the same, and commercially-funded university studies are ongoing worldwide and involve the latest technologies.

Some of the scientific disciplines utilized in the research and development of new personal care products are:

• Biology (understanding hair and skin)

• Microbiology (prevention of microbe growth in product)

• Colloid science (understanding mixtures of waters and oils)

• Physical chemistry

• Biochemistry (proteins, fats, cell membranes)

• Nanotechnology

• Polymer science (synthesizing new polymers for specific uses, understanding how polymers behave in formulas and in situations)

• Processing and engineering (scale-up of a product from lab to commercial production)

• Biotechnology

• Water chemistry (understanding pH, hard water/soft water and the impact that has on products)

• Analytical chemistry and materials characterization (evaluation of raw materials and finished products, including development of novel ways to emulate and evaluate how the product will be used)

Advances in the fields of polymer science in particular have given cosmetic scientists many new ingredients to work with, capable of providing exciting new benefits in the areas of styling, conditioning, moisturizing, and product thickening. Vitamins, herbal extracts, nanoparticles, and other additives have also been gaining popularity with formulators.

Formulators who have added new ingredients to products frequently left many of the old ingredients in the formula. No one wanted to run the risk of decreasing the efficacy of a product or of alienating consumers by changing the product too much. Unfortunately, this led to huge ingredient lists that are expensive to manufacture and final products with very complex behavior. The statistical probability of a complication or problem arising increases with the addition of each new variable. Each new ingredient added to a formula brings with it the potential for interaction with other ingredients, sometimes causing unfavorable results.

In an interview at the Chemists Corner, Dr. Johann Wiechers, an accomplished scientist in the field of skin delivery of biologically active ingredients, discussed how advanced technology is enabling cosmetic scientists to explore the fundamentals of their work at a molecular and mechanistic level. Sophisticated analytical techniques, increased computational capability, and systematic experiments augment knowledge and in some cases have changed ‘the rules’ completely. Hopefully, scientists will use this information to develop new formulas using fewer ingredients, limiting them to the use of only those strategically selected, high performance components. If you care to delve further into this topic, Dr. Wiechers has written a series of articles on the topic, “Is Cosmetic Science Really ‘Bad’?”

In closing, despite its occasionally shaky reputation, I remain in awe of the complexity involved in developing a really good hair or skin care product. While there is certainly an element of art to the development of hair and skin care products, it also incorporates the highest levels of many scientific disciplines

The development of tools by which we can characterize and understand the behavior of cosmetic ingredients and how they interact with skin and hair will inevitably lead to new discoveries and products in the future. As scientists with expertise in different areas continue to collaborate, the consumer will benefit by having access to products specifically targeted to different needs and that provide consistent results. I look forward to reaping the benefits of this work!

Polyquats are cationic polymers, meaning they have positive charges along their backbone or pendant to the chain. They are highly effective as both hair conditioning agents as well as styling agents. These types of molecules can be quite complex in their behavior, and are a subject of extensive study in various fields, including cosmetic science. For this reason (and because I’m a polymer nerd), I find them sufficiently intriguing to revisit the topic fairly often, examining different aspects.

Here at NaturallyCurly.com, we get a lot of questions about polyquaternium ingredients, particularly regarding their removability from hair. Most recently, I read a discussion where the theory was put forth that as long as the polyquaternium number was sufficiently low (say, below -40), then the polymer is fine for use in a shampoo-free or mild-surfactant hair cleansing routine.

Figure 1. Illustration of cationic polymers. a.) linear polymer with charges along the backbone, such as Polyquaternium-10; b.) a comb-shaped polymer, with positive charges pendant to the backbone, such as Polyquaternium-4.

Actually (and perhaps unfortunately,) it is a misconception that one can determine the compatibility of a polyquat and a low-poo method based upon its INCI (International Nomenclature of Cosmetic Ingredients) designation number. This is a logical misunderstanding of how these materials are named. INCI assigns a number to a polymer as it is presented for inclusion into the materials database, in order of submission.

The naming is sequential and is unrelated to molecular structure, molecular weight or charge density. One has to look up the specific polymer in order to obtain its structure. Many of them are structurally quite similar, with various modifications along the backbone, such as the multiple variations of modified cellulose polymer. There are also polyquats made of guar gum, and many others made of various synthetic polymers and copolymers.

Another point of confusion is that the numeric INCI designation does not provide any information regarding the molecular weight of the polymer (the size of the polymer). This property can be quite influential in the performance of the cationic polymer, particularly when it comes to deposition onto the surface of the hair. (Gruber et al, 2001). But the tricky thing for label-readers is that polyquaternium-4 (and all the other cationic polymers) can come in a variety of molecular weights, and there is no way to know which polymer is present without consulting the manufacturer (presuming they would even disclose such information). This could explain why people often observe that they get inconsistent results in very similar products (according to their labels) containing polyquaternium-4 (or -10, or -32, etc.). The polymers may be of substantially different molecular weights, resulting in very different product performance.

Water solubility and build-up:

Cationic polymers can be completely water soluble, or they can be merely water miscible, depending upon things like polymer structure, molecular weight, and charge density. The critical thing to remember is that these polymers perform well as conditioning and styling agents because they are attracted to and adhere to the surface of the hair due to electrostatic interactions (the positively-charged polymer is attracted to the negatively charged portions of the cuticle). The complex that is formed is often very strong, and the interactive forces can be difficult to overcome using conventional methods. A small anionic surfactant such as sodium lauryl sulfate may not be sufficient to overcome that attraction and remove the polyquat.

Polystyrene sulfonate has been found to aid in removal of these polymers from hair, but it is not an ingredient often seen in shampoos. Clarifying shampoos may also not be effective in removing all polyquats from hair. However, some polyquats seem to respond well to traditional shampoos. For instance, researchers at BASF found that polyquaternium-10 is removable with an anionic surfactant.

My personal hunch is that removability is dependent upon the charge density of the polymer (how many positive charges exist along the backbone), its overall structure, and also the state of the hair to which it is applied (more damaged hair has a higher negative charge density, and so would provide a cationic polymer more sites with which to bind tightly). For instance, PQ-10 is a cellulosic derivative, which is very water soluble due to its ether (oxygen-containing) components, which allows for fairly easy removal.

Build-up is also affected by polymer structure. Polyquaternium materials based upon guar gum are more difficult to remove from hair and also display a greater tendency to accumulate on the hair with repeated usage. Polyquaternium-4 is a cellulosic derivative, but with a fairly high charge density. It is extremely substantive to hair and very useful as a styling agent, but has been found to exhibit very little tendency to build up.

I have this other hypothesis that mechanical forces—brushing, washing, combing and styling—are eventually sufficient to detach some of these polymers from the hair. This may be what BASF researchers were seeing when they noticed their new polymer PQ-44 performed very well as a detangler, but did not demonstrate any tendency toward build up. The authors believe that the polymer adheres to the surface of the hair at a few points of the polymer, while the uncharged ends of the polymer form loops that are not flat on the polymer surface. These loops reduce friction between adjacent strands, but also may provide the means for ease of removal later when the hair is washed.

To Polyquat or Not?

In closing, I hope it is more clear now that one cannot rely upon the number of a polyquaternium to determine its removability with any degree of certainty. One has to refer to the INCI database or another source to obtain the exact structure of the polymer in question. Once the structure is known, one can then make certain assessments of its properties.

Although I have seen a few sweeping denunciations of polyquats by some curly hair experts, my personal opinion is that there are certain polyquats that can be advantageous to use in the care and styling of curly hair.

The angled hexagonal structure in combination with the oxygen bonds in the center of the molecule make PQ-10 good for your hair, obviously.

The data indicates that PQ-4, PQ-10, and PQ-44 do not create problems with buildup if one uses a mild shampoo, and each can provide good benefits either in conditioning or styling. There are others that cause more problems with build-up, such as PQ-11 and guar hydroxypropyltrimonium chloride. One recent question was about PQ-37, and while I cannot find specific data on its removability at this time, it looks potentially problematic to me based upon its structure.

As always, choose your products carefully, get samples when you can, and see what works for your hair.

One reader was curious about whether or not showering and swimming were damaging her hair. Specifically, she wanted to know if the water itself was making her hair more brittle and prone to breakage. There seemed to be some confusion about this, so I thought it would be a great topic for discussion, especially in view of the fact that many of us will be wetting our hair more frequently than usual as we swim and sweat our way through the summer months.

The truth is that while we need moisture in our hair in order for it to be healthy, water can also be very damaging to your hair. In fact, the more damaged your hair is, the more damaging water is to it. That may seem a little counterintuitive, so let’s examine the reasons behind that statement.

Normal, healthy hair has been found to absorb up to about 31% of its weight in water when it is immersed. Damaged and very porous hair can absorb in excess of 50% of its weight in water! This water absorption causes hair strands to elongate under the weight of the water and lose some of its tensile strength. Very curly hair has been found to lose almost 50% of its tensile strength when wet, which is really a quite significant reduction.

Water contains things that can GREATLY damage hair.

Due to the loss of tensile strength when wet, hair that is combed or brushed while saturated with water has a much higher risk of breakage. Wet hair is also more prone to tangling due to the slightly raised cuticle surface that is typical for wet hair. For these reasons, it is extremely critical to use plenty of conditioner that has excellent slip properties in order to detangle your hair when it is wet. One good thing that occurs when hair is soaking wet is that it becomes a lot more elastic and stretchy. Combing through your tresses very slowly will enable you to derive the full benefit of the stretchiness of wet hair fibers, which will make the detangling process a bit easier.

Another source of wear and tear on the hair from getting it soaking wet repeatedly comes from the swelling of the hair during the washing/wetting process, followed by uneven shrinking which occurs during drying/evaporation. This creates mechanical stresses on the surface of and inside the cortex of the hair strands and results in gradual fatigue of the fiber, which makes it more likely to fail (break) under stress.

Different types of breakage can occur as a result of this fatigue, such as cuticle breakage, mid-strand fracture, and splitting. Some fatty acids, such as those found in coconut oil, have been found to reduce the effects of this type of wear and tear on hair, so it would seem prudent to utilize them in your hair care regimen, especially if you swim daily or wash your hair very frequently. (The phenomenon of hydral fatigue is described in more detail in this article Mineral Oil Versus Coconut OIl: Which is Better?

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Hard water

The effects of hard water on hair are also difficult to manage and can be quite damaging. Minerals dissolved in hard water deposit onto the surface of hair and after many washings can create a very unpleasant scaly build up. This accumulated layer of hard debris can cause hair to be dry and unruly, tangle easily, appear dull and lifeless, and lead to breakage. If possible, a water softening system can help prevent these issues. However, when that is not feasible, a clarifying shampoo or treatment may be necessary on a regular basis. A weekly rinse with a solution of distilled water and vinegar can be somewhat helpful as well. If you have hard water, expect to need to use larger quantities of conditioner in order to detangle and smooth your hair. Effects of Hard Water and Chlorine on Hair

Loss of fatty acids

Frequent hair washing or swimming in pools or the ocean can lead to a gradual erosion of the fatty acid layer in the cuticle. This can lead to tangling, breakage, loss of surface sheen, and loss of body. Use of gentle products (such as mild cleansers, conditioner washes) can help slow down this process, as can making sure hair is saturated with conditioner prior to swimming. Wearing a swimming cap can also be a great way to protect your hair, but may not fit into your personal style.

In closing, our hair becomes very fragile and vulnerable when it is saturated with water. So, while it is critical to wet and condition our hair in order to detangle and re-moisturize it, and it is also frequently necessary and enjoyable to get our hair wet when we go swimming, it is very important when treat wet hair exceptionally gently.

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Brazilian keratin treatments are a really popular process right now, and are being discussed on the internet, television, and in popular beauty magazines. I must confess that my initial reaction was a negative one, as I found myself thinking “Oh, fantastic; they have found yet another way to reinforce the image of curly hair as the ugly stepchild of cosmetology.” However, once I read some of the personal experiences of fellow curlies, such as that of Michelle Breyer, co-founder of NaturallyCurly.com, I became intrigued and began seeking information about this procedure — particularly information on a scientific and mechanistic level.

What I found was a baffling morass of spectacularly attractive claims, a lot of proprietary ingredients, a whole lot of nothing regarding the actual chemical mechanism by which these processes work, and a lot of controversy regarding the use of potentially harmful ingredients and very high temperatures. A variety of results have been reported, ranging from exceedingly satisfied and ecstatic customers, to those who were mildly disappointed, to a number of consumers reporting dramatic and significant hair loss.

I feel a little like Dorothy setting out on the road to find the Wizard of Oz. There seems to be a lot of smoke and mirrors in use, and I really, really want to know who (or what) is behind the curtain. This article will be my first attempt to penetrate the veil of mystery surrounding these hair treatments. I suspect that some follow-up research will be necessary, and at least one more article on this topic will be in my near future.

Keep the questions coming! Recently, I’ve received inquiries about a couple of sweet botanicals often used in curly hair products. I hope you enjoy this information about agave nectar and marshmallow extract.

Agave Nectar

Agave plant

Agave nectar (or syrup) has become quite popular at health food stores in recent years as a natural alternative to processed white sugar and artificial sweeteners in foods and beverages. Agave nectar is obtained from the agave tequliana, a succulent plant found in Mexico, the southwestern United States, and Central and South America. Yes, this is the same plant that provides us with the infamously intoxicating beverage that yields tasty margaritas and tequila shots—so versatile!

Recently, it has also become trendy to incorporate agave nectar into hair care products, especially homemade concoctions such as flax seed gel and oil-based hair conditioning treatments. As a result, I have gotten a few questions regarding this ingredient and how it compares to other natural ingredients used for similar purposes, such as honey. As always, the answers are to be found in the chemistry.

Agave nectar is composed of several large carbohydrate molecules called polysaccharides: saponin, inulin, and fructosan. These polymers are made up of building blocks of different types of sugar molecules. Fructose is the primary component, with glucose being a smaller fraction of the material. Polysaccharides have many hydroxyl groups and for this reason are very hydrophilic. They will behave as humectants and draw water either to the hair or out of the hair, depending upon the environment. (To learn more about the ramifications of humectants and curly hair, see Humidity, Humectants and Hair.)

In most instances, raw agave is refined prior to being made available as a sweetener or a beauty product ingredient. In this process, the polysaccharide molecules are hydrolyzed and broken down into the small molecule simple sugars (glucose and fructose) that are the building blocks of the polymers. Refined agave nectar such as this will have very similar effects on hair as honey, due the size and molecular structure of the components. (For more information about honey, check out The Buzz About Honey.)

Raw agave, which contains a much higher percentage of polysaccharides, should behave a little differently than honey when used on hair. Raw agave nectar can provide conditioning by forming a polymer film on the surface of the hair, thereby smoothing the cuticle. It can also provide mild hold, due to the polymeric structure of its unaltered carbohydrates. Unrefined agave nectar also contains minerals such as iron, calcium, potassium, and magnesium, which may be beneficial to hair. For these reasons, I highly recommend seeking out raw, organic agave nectar to use in your homemade styling and conditioning products, as it can augment the performance of your product more than refined, processed agave.

Marshmallow Extract

Marshmallow plant

Another plant-derived ingredient about which I have received some questions is marshmallow extract or marshmallow root extract. Marshmallow root extract is derived from the herb Althaea officinalis, a plant that has long been valued for its medicinal properties. The extract bears no relation to the sticky white treats by the same name. (No one actually thought for a second that those might be “natural” or plant-derived, did they?)

Similar to agave nectar, marshmallow root extract is composed of polysaccharides—more complex sugars and also mucilage components, which contain both sugars and proteins.

Polysaccharaides and mucilaginous molecules are film-forming polymers when applied to hair, which makes marshmallow quite useful as both a conditioning agent and a styling agent. It has emollient properties and can help with detangling as well.

Many plant-derived substances have such great potential for use in both hair and skin care. They are also considered to be more earth-friendly in terms of the processing required, and some consumers feel safer using them as well. I find the biochemistry fascinating, and I think it is wonderful to see them being used more often. Understanding how they work and what we can expect from them is the key to getting the best results. Enjoy—but just don’t try to sweeten your coffee with your hair gel.

Last month’s article delved into the chemistry and properties of mineral oil, as well as some of its benefits and drawbacks when used as an ingredient in hair products or as a topical treatment. This month, I would love to expand on that topic a bit and dig a little deeper into the similarities and differences of petroleum-derived mineral oil and plant-derived oils, specifically coconut oil. Both types of oils are found in various hair care products, and coconut oil is quite often used in homemade treatments, as well. The superior properties of natural oils are frequently lauded, so it should be interesting to review a few scientific comparisons backed by data.

Water in – water out

Several published studies have summarized experiments done to evaluate and compare the emollient properties of mineral oil, coconut oil, and to a lesser extent, olive oil and safflower oil. In one paper, researchers reported using an analytical technique (dynamic vapor sorption, for those curious) to measure and determine the moisture diffusion coefficient for mineral oil, coconut oil, and other oils when applied to hair. They were interested in finding out was how much water vapor can penetrate into or diffuse out of hair that has been coated with oil.

The data obtained in the experiments revealed that both coconut oil and mineral oil form a protective barrier that effectively prevents the diffusion of moisture out of the hair in low-humidity environments, thereby improving moisture retention and minimizing dry, fly-away hair. All of the oil-treated hair samples showed this effect, whereas the untreated control remained unchanged.

It was noted that for coconut oil, the moisture-retention effects dissipated significantly over time. This is credible evidence that coconut oil absorbs into the hair shaft while mineral oil remains on the exterior surface. (Remember this—it will be important later).

All of the treated hair fibers showed a reduction in absorption of moisture vapor from the atmosphere in damp conditions. This is advantageous in an anti-humectant topical treatment, as it provides some protection from frizz that often occurs in high relative humidity. However, this effect was not total, and each sample was found to absorb significant amounts of water over time. Extremely hydrophobic mineral oil performed the best in terms of its ability to seal water out of hair, while the more polar fatty acids such as coconut oil allowed greater transport of moisture through the cuticle and into the hair shaft. This can certainly be an undesirable attribute if frizz and the tell-tale halo are not qualities you prefer in your hair.

Curl Formation and Clumping

Both coconut oil and mineral oil enhance clumping of adjacent hair strands. This mechanism aids in curl formation, definition of curl pattern, and curl retention. Capillary adhesion, the mechanism by which this is possible, occurs when oils form sufficiently thick films on the surfaces of hair strands and capillary forces between adjacent hairs attract them to one another, effectively binding them into clumps.

Researchers found that capillary adhesion between hair fibers remains constant with mineral oil, but is found to decrease over time with coconut oil, olive oil, and sunflower oil. The reason for this is that the very non-polar mineral oil molecules remain on the surface of the cuticle of the hair. In contrast, the saturated or mono-unsaturated fruit and vegetable oils in this study slowly penetrate into the cell membrane complex (CMC) and are transported into the hair shaft. As this diffusion occurs, the film thickness on the surface of the hair gradually decreases, which diminishes capillary forces. As a result the cuticle scale structure begins to dominate the behavior of the surface of the hair once more, and subsequent tangling and frizz can occur.

A Closer Look at the Penetration Behaviors of Mineral Oil and Coconut Oil

As you have probably ascertained from this article, many of the behaviors and performance of oils and moisturizers on the hair are affected by whether they remain on the surface or are absorbed into the hair. To get a more quantitative understanding of this, scientists performed direct study of the penetration behaviors of coconut oil and mineral oil on hair via spectrometry (secondary ion mass spec (SIMS) plus time-of-flight mass spec (TOF-MS). The results showed definitively that coconut oil does indeed penetrate the hair shaft, while mineral oil remains on the surface of the air.

Both mineral oil and coconut oil have pretty compact structures which should physically permit diffusion through the porous external layer of the hair shaft. So why does coconut oil do so, while mineral oil does not?

The answer lies in the atoms. While the chemical structure of the molecules present in mineral oil is purely carbon and hydrogen, rendering them very non-polar, triglycerides such as those found in plant-derived oils contain carboxylic acid groups, which lend a little polarity to the molecules. This polarity confers an affinity to these oils for other polar molecules, such as the various keratinous proteins of which hair is comprised. Thus, it is this inherent attraction to other polar molecules, coupled with the relatively simple structure of coconut oil that enables it to diffuse through the cell membrane cortex of the hair and penetrate into the central cortex. Mineral oil has no such affinity for proteins, and remains on the more hydrophobic exterior surface of the hair.

Coconut oil and improved resistance to wash-wear

The presence of coconut oil inside the cortex of hair provides multiple benefits. It acts as a plasticizer to soften the hair and provide more flexibility and toughness. Coconut oil also increases retention of keratin molecules within the hair shaft, which reduces protein erosion that normally occurs during wash cycles. Continuous loss of protein over time from routine washing damages hair and can result in color fading, split ends, and breakage, so anything that can moderate this phenomenon is beneficial.

An additional advantage to coconut oil inside the hair shaft is that it decreases the amount of swelling of the hair shaft that normally occurs when immersed in water. Normally, when hair is saturated with water during the washing process, it absorbs up to 30% or more of its weight in water. This causes each strand to swell considerably, which can lead to several undesirable effects. Increasing the diameter of the hair shaft causes the outer covering of cuticle scales to lift and separate, which increases tangling and breakage. But, perhaps more subtle, is the damage done over time from many cycles of expansion and contraction.

Hair is a highly complex biomaterial composed of layers of differing materials, ranging from varying types of keratin structures to pigment molecules to fatty acids. When it is saturated with water and swells and then subsequently dries via natural or thermal means, it undergoes what is known as differential drying and differential deformation (because each separate type of molecule within the overall structure dries and deforms at differing rates). This leads to moisture-induced stress on the hair, which can lead to delamination (cuticle layer stripping off), breakage, fiber fatigue, and rupture (split ends). This whole phenomenon is referred to as hygral fatigue. So, anything that reduces hygral fatigue is great for the health of your hair in the long term.

Which is the winner?

Well, both water insoluble oils have some distinct advantages for curly hair. By improving moisture retention within the hair shaft, they each can minimize drying and frizz which may occur in arid climates. Both enhance curl formation and clumping. However, in both of these things, mineral oil does the job better and for a longer time. On the other hand, coconut oil appears to have some real potential for improving the health and long-term vitality of hair, especially when it comes to wash-wear, whereas mineral oil is more of a topical treatment that is effective until it is washed away. Those with very porous hair may find that coconut oil penetrates too much into the interior of the hair, which can cause its own set of problems such as frizz, greasiness, and limp hair. So, adding either coconut oil or mineral oil to your hair care regimen may prove to be beneficial, but proceed with caution and see what works best for your own locks.

Mineral oil has been found in cosmetic and personal care products for 100 years or more, because it is an excellent lubricant that is lightweight and non-greasy. However, in recent years it has really fallen out of favor with consumers for a variety of reasons, among them being concerns about safety. It may also have been a victim of negative marketing simply because it is unpretentious and cheap, which is not necessarily advantageous to companies spending time and money developing new materials for hair care. Let’s take a closer look at mineral oil and see what it is, where it comes from, and what it does for hair, so we can make informed decisions without the influence of marketing agendas.

What is Mineral Oil?

Mineral oil is a mixture of simple hydrocarbon molecules of varying molecular weight derived from the petroleum cracking process. It is a cheap byproduct found to be easily purified and useful in a variety of applications for which a lubricant is needed. Mineral oil is a mixture of medium-to-long chain alkanes (15 – 40 carbons) with the general formula of CnH2n+2. There are no other elements present in mineral oil. The molecular structure of these materials is very uncomplicated, extremely stable and nonreactive.

Petroleum Cracking

Crude petroleum is a huge organic soup, containing many different carbon-based molecules of varying molecular weights. The petroleum cracking process uses thermal and other catalytic means to break these molecules down into lighter, smaller molecules such as octanes, which are highly desirable as fuel because they are easily combustible and fairly efficient. Other components, such as larger hydrocarbon molecules that comprise mineral oil, paraffin wax, and petroleum jelly, are byproducts of this process and are separated out via distillation. More dangerous byproducts of the petroleum cracking process, such as benzene, are easily separated out due to the large differences in molecular weight.

PQ-68

Some of you may know that my main passion in the world of chemistry and materials is for polymers. I frequently peruse the literature looking for interesting new polymers or old ones being used in new applications, especially in the field of hair and skin care. Recently, I was doing some research on a few newer cationic polymers (of the INCI : polyquaternium-xx family), when I ran into one that I found fascinating, especially for curly-haired consumers. Its industry trade name is Luviquat Supreme, and it is manufactured and distributed by BASF Corporation. The INCI designation for this polymer is Polyquaternium-68 (PQ-68).

The polymer nerd in me was intrigued by the complex structure of this molecule (see below). It is a synthetic quaternized copolymer comprised of 4 different monomers (vinylpyrrolidone (VP), methacrylamide (MAM), vinylimidazole (VI), and quaternized vinylimidazole (QVI)), with an average molecular weight of around 300,000 grams/mole. It has positive charges along the polymer backbone, which give it the ability to spread easily onto the surface of hair and form a film that adheres to it. Its physical structure is such that it is a very stiff molecule. When polyquaternium-68 is applied to hair in a styling product, the resultant encapsulating film smooths the cuticle, providing mild conditioning properties, and also imparts body and structure (style) to the hair.

The inflexible molecular structure of Luviquat Supreme gives the polymer a very high degree of stiffness (measured on films and reported as Young’s modulus). This property allows it to impart very strong hold to hair. The inherent rigidity of PQ-68 means that significantly less polymer is required in a product to get the same amount of hold as other common styling polymers such as PQ-4, PQ-11, which makes using the specialty polymer more affordable. Formulators can also tweak the amount of hold their product provides, simply by adjusting the quantity of polymer in the formulation or by adding small molecule ingredients used to soften the films (called plasticizers).

Luviquat Supreme is particularly advantageous when used in styling products designed for curly hair. Its physical properties make it excellent at curl formation as well as curl retention. Due to its chemical structure, it provides nearly 100% hold and curl retention in extremely high humidity, and far outstrips the performance of other traditionally used styling polymers (tested at 90% RH, compared to PQ-4, PQ-11, PQ-55, and PVA/VP). It also does not get that sticky, tacky feeling that many other polymers get in humid conditions. An additional benefit to curlies is that, despite its outstanding moisture resistance in humid weather, PQ-68 is completely soluble in water. So it is extremely friendly to low-shampoo and no-shampoo routines!

A Synergistic Combination

When a film formed by a styling polymer is too stiff, it can feel unpleasant and yield a sensation of “crunchiness” which some consumers dislike. Also, a very stiff film is typically brittle and can break into tiny pieces, resulting in an annoying flaking problem common to many gels and mousses. In an effort to remedy this drawback, small molecules such as propylene glycol and panthenol are often added to styling products. Their presence in the composition acts to soften the film formed by the polymer. However, in formulation, there is often a give and take when combining ingredients, and the addition of an ingredient to achieve a desirable property often results in a new undesirable property or loss of performance. It is a tricky business.

Well-aware of this formulating conundrum, researchers at BASF were pleasantly surprised by properties obtained when they combined PQ-68 with panthenol. Not only did the panthenol soften the film and add shine to the hair, but it also enhanced some physical properties while preserving many of the original desirable properties. When they performed tensile testing, they found that the flat film stiffness was decreased as expected, but that the elasticity of the film was exponentially increased. Similar testing was performed on treated swatches of hair, and the data showed that the hair strand stiffness was not significantly affected, but that curl retention was enhanced. Remarkably, the presence of panthenol in the films did not deteriorate the excellent humidity resistance of the product.

What this means is that this PQ-68 + panthenol combination allows for exceptional curl formation, curl hold, and curl retention. When a curl is deformed by touching it, by wind forces, or by wearing a hat or scarf, a brittle film might break and the style will be lost. However, a highly elastic film will bounce back when the force is removed. This is exactly what researchers found to happen with this ingredient combination. The same experiment performed with other polyquaternium materials plus panthenol did not produce the same results, so there is something unique going on between these two molecules.

The Polyquaternium-68/ Panthenol combination is found in the following products:

• Fekkai, “MORE” All-day density styling whip, formulation appears fairly CG friendly
• Rene Furterer Volumea Volumizing Mousse, formulation may be potentially drying due to higher quantities of alcohol
• Zero Frizz Curl Rescue Perfecting Spray
• David Babaii for WildAid, Amplifying Whipped Mousse—formula contains many natural oils in addition to the “magic combo” and looks very promising
• Nivea, Flexible Curls Styling Mousse

Clearly, this ingredient combination seems to work well in mousses and styling foams. There are several sample formulations provided at the raw material manufacturer’s site (BASF) for making them. However, I would like to see the polymer used in a gel product, as that is a styling product that seems to be preferred by many of us with curly hair . I was wondering if that was possible due to potential gel clarity or water solubility issues, and then I found this gem: Hair styling composition, USPTO Patent Application 20090226390

In this 2009 patent application, the inventors make a number of claims for incorporation of PQ-68 and PQ-4 into a clear, sprayable styling gel. The descriptions states that an aqueous-based, alcohol-free, formulation containing a mixture of polyquaternium-68 and polyquaternium-4 formed a sprayable gel with a high degree of clarity. This gel was found to spread most easily on damp or wet hair, which facilitated adhesion between hairs. The composition provided firm, yet flexible hold, that was long-lasting and resistant to humidity. It sounds perfect! I have yet to locate a commercially-available gel product with this composition, but I expect (hope) we will be seeing it soon (especially once this patent application is approved).

I think that the polymer research team at BASF has really hit upon an unexpected winner in polyquaternium-68 (Luviquat Supreme), especially for those of us with curly hair. I hope to see this ingredient, along with panthenol, included in more curly hair styling products as hair care formulators start to experiment with it.