Cosmetic Excipients: Surfactants Used in cosmetic formulation

Cosmetic excipients used in the preparation of various skin care, hair care and oral care formulations.

1. Cosmetic Excipients: Surfactants Dhanshri O. Tikekar,  Dipti A. F ating Subject : Cosmetic Science,             B. pharm final year Guide name : Chandrashekhar M. Chakole Bajiraoji Karanjekar College of Pharmacy, Sakoli,   Dist : Bhandara . M.S.-441802 Rashtrasant Tukadoji Maharaj Nagpur University

2. Contents What is surfactant? Structure of surfactants Mechanism of action of surfactants Tyes of surfactants Properties of surfactants Applications of surfactants  Reference 

3. What is surfactant?

4. 2) Structure of surfactant: The surfactant molecules are characterized by having two groups in their molecular structure. Hydrophilic head and hydrophobic tail both are important determinants of lowering surface tension. The hydrophilic group (water-attracting group)has an affinity for water and have strong affinity for solvents. They can be neutral or charged. Hydrophobic group (water repelling group) such as hydrocarbon chain that has no affinity for aqueous solvents.

5. 3) M echanisms of action of surfactant: There are three mechanism s of action of surfactants, and they are as follows: Roll-up mechanism:  Adam in 1937, first proposed the roll-up mechanism. To remove the oil droplets from a rock surface the roll-up mechanism is a good way.  When the contact angle is between the aqueous phase and the substrate decreases, the roll-up mechanism occurs. Emulsification: The surface-active agents reduce the interfacial tension between oil and water and make the emulsification of oil and water. Solubilization: In this mechanism, through interaction with the micelles of surfactant in the aqueous phase(water), the substance gets dissolved to form a stable solution without having any impurity. The micelles work as a unit to remove the dirt. The hydrophobic tails get attracted towards soils and surround them; on the other hand, the hydrophilic heads pull the surrounded soils from the surface into the solution.

6. 4) Types of surfactants: Surfactants are classified based on their polar head. The hydrophilic head of the surfactants has a charge with some kind of charge. The charges can be negative(anionic), positive(cationic), or neutral. Some surfactant consists of two opposite charges. If the head of the surfactant carries a positive charge, then it is classified as a cationic surfactant. If the surfactant head carries a negative charge, then it is classified as anionic surfactant. If the surfactant head does not carry any kind of charge, then it is called a non-ionic surfactant. If the surfactant carries both negative and positive charge, then it is classified as amphoteric surfactant.

7. Cationic surfactants Cationic surfactants are agents which are composed of polar and non-polar parts. The polar part of these agents is always composed of a quaternary ammonium unit. Cationic surfactants are ineffective as detergents in cleansing systems because they bear positively charged groups on their polar head. These positively charged surfactants are primarily used in conditioners. Cationic surfactants are well known for their conditioning effect as th ese surfactants bond to the negatively charged hairs. Examples are benzalkonium chloride, methylpyridinium chloride, cetrimide stearyl alkonium chloride, etc. 

8. Anionic surfactants Anionic surfactants are organic substances. When these surfactants are dissolved in water, they produce negatively charged particles, called anions.  Anionic surfactants are strong cleaners . They are excellent at removing sebum and dirt . Anionic surfactants can be produced from a variety of raw fats and oils, including soybean, tallow, palm and coconut.  Examples are Sodium lauryl sulphate, sodium lauryl ether sulphate, sodium cocoyl sulphate, and ammonium lauryl sulphate.

9. Non-ionic surfactants Non-ionic surface-active agents are neutral in nature as they do not have any kind of charge on their hydrophilic head. These surfactant refers to the molecules which do not undergo ionization when dissolved in water. These surfactants are gentler than anionic surfactants and are very good at emulsifying oils and better at removing organic soils. Certain non-ionic surfactants are non-foaming or low-foaming which makes them a good choice as low-foaming detergent. Examples are Cetyl alcohol, stearyl alcohol, cetostearyl alcohol, lauryl glucoside, glyceryl laurate, polysorbates, spans, and Poloxamers.

10. Amphoteric  surfactants The se are the surfactants which consists dual charges i.e. both positive and negative charges on their hydrophilic end. These dual charges cancel each other hence the net charge is zero. This is known as zwitterion. The amphoteric surfactants become positively charged and behaves like cationic surfactants in acidic solution while in alkaline solution they become negatively charged and behave like anionic surfactants. The  characteristics of amphoteric  surfactants are better emulsification and dispersion, excellent smoothness and softness,  acts as  an antistatic agent to the fabrics, etc. Examples are Cocamidopropyl betaine, sodium cocoamphoacetate,  alkylamidopropylamine N-oxide(APAO).  

11. 5) Properties of surfactants: Decreasing surface tension : Sur f actants have the good property of lowering surface tension between two liquids or between a solid and a liquid. This property allows the surfactants to penetrate through the surface and spread evenly on the surface. It allows the proper mixing of various types of molecules. Dispersing : I n this phenomenon, the non-polar substances form the tiny particles in water and get evenly dispersed. Surfactants enhance the dispersion process. The efficiency of the dispersion process is mediated by the surfactant’s interaction with the material and the structural features of the surfactants like the charge of the polar group and its type,  and length of the alkyl chain. Softening: Surfactants have good softening properties. The surfactants having excellent softening effects are preferably used as a conditioning agent in shampoo and conditioners. Mon alkyl and  dialkyl quaternary ammonium salts, and alkylbenzyl quaternary ammonium salts are most commonly used in cosmetic preparation. 

12. Cloud point : C loud point is also called a lower consolute temperature. It refers to the phase transfer of non-ionic surfactants. In this phase transfer system, the clear homogeneous solution is converted into a cloudy solution. Micellization : It is the dynamic process in which monomeric surfactant molecules aggregate into a discrete structure.   Th e concentration at which micelles appear at the given temperature is known as critical micelle concentration. Wetting and penetrating : Surfactants reduce the cohesion between the water molecules and penetrate through them. This process lowers the energy difference between the water and the pigment and also reduces the surface tension. Surfactants with good wetting and penetrating properties spread evenly and can enhance the cleaning, dispersion and emulsification process. 

13. 6) Applications of surfactants:  Surfactants in hair care: Detergency of surfactants id depends on the length of hydrocarbons. Shorter chain-length surfactants have stronger grease-removing properties. Long-chain surfactants improve mildness and reduce lathering properties.  Shampoo: Shampoo is the widely used hair care preparation in the market of hair cosmeti cs. Surfactants in shampoo formulations form micelles and wash out the dirt and oil from the hairs. Anionic surfactants are generally used in shampoos they provide lather and detergency to the shampoo. Conditioners : Conditioning surfactants are the opposite of shampoo surfactants as they deposit on the hair. In hair conditioners, cationic surfactants are mainly used as they are positively charged. These surfactants are meant to adsorb on the shaft of the hairs rather than being washed off.

14. Surfactants in makeup and skincare: Surfactants are an important part of the skincare and makeup industry. In skincare products, surfactants are used as emulsifiers for the formulation of different creams, lotions body washes, etc.  Lotions and creams: lotions and creams are applied to soften, smooth and moisturize the skin. Polyethylene glycols are essentially used as the base for creams and lotions. PEGs are compounds which are used as thickeners, solvents, and softeners also they are good at carrying moisture. Body washes: surfactants are the essential components in body washes. Surfactant’s job is to clean the skin by removing hydrophilic dirt and naturally produced oils from the body. Surfactants act as the cleansing agent in the body- washes as they pull off oil-based dirt and microbial contaminants from the body.

15. Surfactants used in oral hygiene : Surfactants are commonly used in oral hygiene formulations like mouthwashes, and kinds of toothpaste. In oral hygiene products they act as solubilizing, wetting and dispersing agents and give the foaming effect. Toothpaste: surfactants reduce the surface tension of the watery environment of the oral cavity so the toothpaste can contact easily with the teeth. They help to loosen the debris and plaque and make the cleaning process easier.  Mouthwashes : Mouthwashes used for cosmetic purposes are prepared to reduce bad breath with the help of flavouring and antimicrobial agents. Surface active agents are used in the mouthwashes because they help in the solubilization of all the flavours and remove the debris by producing foaming action.

16. Conclusion Surfactants play a vital role in various cosmetic and personal care products due to their unique properties. Their ability to lower surface tension, emulsify, solubilize, disperse, and wet surfaces makes them indispensable ingredients in formulations like shampoos, conditioners, creams, lotions, body washes, kinds of toothpaste, and mouthwashes. The different types of surfactants - anionic, cationic, non-ionic, and amphoteric - offer specific functionalities tailored for different applications. Anionic surfactants provide excellent cleansing and foaming action, while cationic surfactants impart conditioning effects on hair. Non-ionic surfactants are mild and effective emulsifiers, and amphoteric surfactants offer versatility by behaving as either anionic or cationic depending on the pH. The choice of surfactant and its concentration in a formulation significantly impacts the product's performance, mildness, and sensory attributes. Careful selection and blending of surfactants are crucial in creating effective and consumer-pleasing cosmetic products. As cosmetic science continues to evolve, surfactants will remain essential ingredients, driving innovation and meeting the ever-changing consumer demands for high-performance and multifunctional cosmetic products.

17. 7) References Wilkinson, Moore, (1982), Harry’s Cosmeticology , Seventh edition, Chemical Publishing, USA. P-633-640. Sharma P.P. , (2014), Cosmetics – Formulation, Manufacturing and Quality Control, Fifth edition, Vandana Publication Pvt. Ltd., Delhi. P-94-103. Pathak . K., and Vaidya A., (2018), A textbook of cosmetic science concepts and principles, First edition, Nirali Publication, Pune. P- 3.1- 3.4. Singh S.P., a nd Nigam V., (2021), Cosmetic Science textbook, First edition, Thakur Publications Pvt. Ltd. Lucknow.  P -2 2-23. Mehetre G.D., Ambhore J.P., Cheke R.S., Shinde S.D., (2022),Cosmetic Science, First edition, S. Vikas and Company (medical publishers), Jalandhar. P-9-22.

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