Lip gloss, one of the most common, simple cosmetics used by girls and women all over the world, is much more complex than one might think. By breaking lip gloss down into its chemical compounds, one begins to see the intermolecular forces at play. These forces culminate and interact, allowing lip gloss to exhibit its useful and beautifying properties.
How does lip gloss stay on your lips and prevent chapped lips, and why is it so popular in today’s culture?
We decided to make lip gloss ourselves to see how the intermolecular forces take place as the ingredients are combined. Check out our video
Since the evolution of mankind, humans have had to deal with a very serious epidemic… dull, chapped lips. Characterized by cracking and peeling of the the lip epidermis, chapped lips may be caused by licking one’s lips or dry and windy weather. This painful nuisance is a problem that people have been trying to solve for centuries. The result: the creation of lip gloss. First invented in 1930 by Max Factor for the movie industry, this product has become a valuable tool to combat chapped lips and to addbright color to one’s lips.
But how is lip gloss able to solve this problem? It is all due to the chemistry behind the substance.
Lip gloss is most commonly composed of wax, petroleum jelly, oil, polybutene, color additives, and fragrances. Each ingredient plays an important role in determining lipgloss’ overall properties. Many makeup companies also add ingredients used to nourish the skin, such as vitamin A, C, and E, and natural plant extracts. Preservatives are used to elongate shelf life and to prevent bacteria growth. Color additives make the product match the consumer’s preference (less than 5% of ingredients), and added fragrances give the lip gloss a more pleasant smell. The combination of wax, jelly, and oil takes up over 50% of the ingredients.
The ratio of these three ingredients controls the form and solidity of the lip gloss. For example, creamier lipgloss, generally found in jars rather than tubes or sticks, contains less jelly and wax and more oil.
Petroleum Jelly: Refined and processed from crude oil, petroleum jelly is made of a chain of non-polar hydrocarbons. It is made of both mineral oil, and paraffin and microcrystalline waxes. The waxes used in lip gloss can also be derived from petroleum. Petroleum jelly provides a good base for the lip gloss because it is chemically inert. Since it is made of hydrocarbons and there are no dipoles, the only force occurring in this substance is London Dispersion Force (LDF), which is stronger because of the long chain of hydrocarbons, creating a melting point up to 75°C. London dispersion forces occur when the electrons of a molecule are arranged so that the electron density on one side of a molecule or atom is much greater than that of the other side of the atom. A partial negative charge forms within the atom or molecule where the electrons are clumped together, while a partial positive charge forms on the other side, where the positive charges of the protons in the nuclei are more abundant. This forms a dipole within the atom or molecule itself, and this allows for attractions to occur between nonpolar molecules. Unless an emulsifier is mixed in, petroleum jelly is hydrophobic because the molecule only contains hydrogen and carbon atoms. It is attracted to other nonpolar regions, and therefore, the oxygen in water, which is a polar molecule, does not attract the LDFs in the jelly. Consequently, LDFs create hydrophobic interactions.
Oil: Oils such as olive oil, coconut oil, and cocoa butter come from plant or mineral sources and help the gloss to stay on the lips. Oils also ensure that the lips stay moisturized. The molecules of oils consist of many carbon-hydrogen molecular bonds. These carbon-hydrogen bonds are nonpolar, meaning that the two atoms share electrons equally; in other words, they have an equal pull on the electrons in the bond, causing these sections of the molecule to lack adipole-dipole intermolecular attraction. Therefore, other forces mustbe present to keep these molecules attracted to each other, and these forces are London dispersion forces. London dispersion forces are particularly important in the relatively massive molecules of oils, as more electrons and protons are present in a single molecule. Since oil molecules are nonpolar, they will not dissolve in the polar molecules of water, making oil hydrophobic.
Wax: Waxes, such as beeswax, carnuba wax, or candelilla wax, help to build viscosity and extend wear. The molecules of waxes typically found in lip gloss are composed of ester and alcohol groups, in addition to many carbon-hydrogen molecular bonds. The presence of the ester and alcohol groups allows part of the molecule to be polar. Therefore, the alcohol ends participate in dipole-dipole intermolecular forces. Specifically, these groups form hydrogen bonds with other molecules since the hydrogen is bonded to the highly-electronegative oxygen. These intermolecular forces occur because the hydrogen holds a partially positive charge, since the oxygens of the alcohol groups have a stronger pull on the electrons in the bond. Thus, the hydrogens can attract the partially negative atoms of other polar substances, such as the oxygens in water molecules. However, the section of the molecule containing hydrocarbons is nonpolar. Therefore, London dispersion forces will allow this end of the molecule to attract other nonpolar molecules. Although some wax molecules are overall polar, their separate sections allow them to act as emulsifying waxes, which will be explained later in this post. Other waxes in lip gloss, such as paraffin wax, may only consist of carbon-hydrogen bonds. Thus, not all waxes are emulsifying waxes. Instead, they are nonpolar materials that help to establish the texture of the lip gloss.
Polybutene (C4H8): a liquid used to create the shiny quality of lip gloss.
Vitamins and Extracts: used for health and healing and antioxidant properties.
What’s an emulsifier?
Lip gloss is made up of both hydrophobic (“water-hating”) materials such as oils and hydrophilic (“water-loving”) materials such as aloe-vera. Hydrophobic substances lack the ability to form intermolecular attractions with water, while hydrophilic substances are polar and mix with water-based substances. If lip gloss contains both hydrophilic and hydrophobic substances, how is it possible that all substances, even the immiscible ones, mix to form homogeneous lipgloss?
Well, lip gloss is an emulsion. In an emulsion, the hydrophobic materials attach to the emulsifier and divide into many microscopic micelles. In lip balm and lip gloss, polysorbates, ethoxylated alcohols, and sorbitan esters are typically the emulsifiers. Emulsifiers have a “head” that is strongly polar and a “tail” that is a non-polar hydrocarbon. A micelle is formed because the hydrophilic head is attracted to water while the hydrophobic tail is attracted towards the oil. With this arrangement, the amount of nonpolar molecules exposed to the water is reduced, thus reducing the hydrophobic effect.
Here, hydrophobic droplets of oil are suspended among the hydrophilic substance of water. It is clear that the two substances do not readily mix, making the presence of an emulsifier necessary.
This image represents a micelle. The orange sections represent the hydrophobic tails and the gray dots represent the hydrophilic parts of the emulsifier.
This illustrates the effects of an emulsifier, which allows the oil to be homogeneously suspended throughout the water. Added emulsifiers in lipgloss readily mix hydrophobic and hydrophilic substances.
The various compounds combine to make lip gloss as perfect as it is today. Waxes thicken the solution while the oils moisturize the skin. The emulsifier allows the solution to all mix together. The long hydrocarbon chains in petroleum jelly allows the lip gloss to lock the moisture on the lips so they do not become dried out. Van der Waal’s forces relate to the non-polar attractions between molecules due to transient polarization of electron clouds. Though LDF is one of the weakest forces, it is most prominent in lip gloss by preventing water molecules from passing through the solution and being evaporated. The wax and grease molecules interact to form this solid water barrier. Thanks to chemistry and the invisible forces between different liquid and solid molecules, the chapped-lips epidemic has been solved!
Stay updated for our next blog post about the chemistry of mascara!