Amodimethicone: A Star Silicone in Haircare

Figure 1

Written by Abida Mozid

Haircare is an industry worth billions in revenue. With a broad spectrum of products constantly marketed to consumers, it can be overwhelming to understand which are worth shopping for. An alternative approach supported by science can be applied to discern through the many trends and branded sponsorships.

This article will introduce this approach by discussing a staple in the beauty industry, one found in the majority of cosmetic ingredients lists - silicones. In particular, one named amodimethicone. 

Silicones and Amodimethicone - What Are They?

Silicones are a class of artificial polymer made from the element silicon. In cosmetic chemistry, silicones are made up of organic side-groups bonded to repeated silicon-oxygen (Si-O) bonds (siloxane bonds). ⁽²⁾ Due to the repeated siloxane bonds, silicones display multiple behaviours, including chemical stability, water resistance, flexibility and the ability to spread easily over surfaces. ^{(2, 4, 13, 10, 16)}

In hair care products, silicones are used as film-forming conditioning agents. They provide a thin and smooth covering over the hair shaft, helping to shield the hair fibre from heat, humidity and mechanical damage. ^{(2, 4, 13, 10, 16)}

Different silicones exhibit distinct behaviours. Amodimethicone is a silicone which is chemically altered to engage specifically with damaged hair strands.

Amodimethicone is generated from the silicone named polymer polydimethylsiloxane (PDMS). This is a member of the class of silicones known as amine-functionalised silicones. This molecule has amine groups (NH or -NH2) in place of some methyl groups on PDMS. ⁽³⁾

Figure 2: Structural representation of amodimethicone, consisting of a linear polysiloxane siloxane (-Si-O-Si-) backbone composed predominantly of dimethylsiloxane repeating units (indicated by x). Proportion of siloxane units (indicated by y) are substituted with aminopropyl side chains terminating in primary/secondary amine groups. Polymer chain shown with terminal hydroxyl (-OH) function. ⁽⁵⁾ 

Under mildly acidic conditions, such as many conditioning formulations, these amine groups acquire a positive charge. Due to this, amodimethicone displays cationic behaviour, so it is drawn to negatively charged surfaces, such as hair fibres, especially damaged hairs. ⁽⁴⁾

Hair Structure and Damage

So how does amodimethicone operate within haircare? To understand how it benefits hair, it is important to first understand the structure of the hair fibres.

A single hair strand consists of multiple layers:

• The cuticle - this is the outermost protective layer that forms overlapping ‘scales’ made up of the cuticle cells. ⁽⁶⁾

  
  

• The F-layer - a lipid coating on the cuticle mainly containing 18-methyleicosanoic acid (18-MEA). This offers hydrophobic (repelling water due to non-polarity) protection. ⁽⁶⁾

  
  

• The cortex - this is the core which contains keratin proteins as its main component. The keratin is structured by different chemical bonds, with the disulfide bonds, which are the inter-chain bonding between cystine amino acids, being the strongest and defining the hair structure. ^{(7, 10)}

  
  

• The medulla - this is the innermost layer of the hair shaft, located beneath the cortex. It consists of keratinised cells with spaces of air between them. These medullary cells are irregularly organised and therefore, they can even be absent in finer hairs. ⁽⁸⁾

Figure 3: Schematic cross-sectional representation of a human hair fibre, displaying the outer cuticle consisting of overlapping layers (approximately 6-10), the inner cortex beneath containing keratinised cells, and the innermost central medulla. ⁽⁹⁾

How Do Silicones Impact the Hair?

Conditioning products are used to prevent damage and support with repairing the hair structure.

Processes such as:

• Bleaching and/or hair colouring ⁽¹³⁾

• Heat styling ⁽¹¹⁾

• UV exposure ⁽¹⁴⁾

• Mechanical friction ⁽¹⁵⁾

  
  

all gradually diminish the protective lipid layer, leaving the underlying protein core vulnerable. The surface of the hair then becomes more negatively charged. ^(17,19) This can cause the cuticle to appear rough or raised, and the fibre turns more porous and sensitive to environmental moisture. All these alterations are what causes issues such as frizz, tangling, dullness and breakage. ^{(10, 16)}

Mechanism of Amodimethicone

• Electrostatic Attraction

Amodimethicone is positively charged when formulated into conditioners, so it is electrostatically attracted to the negatively charged areas of damaged hair. Therefore, amodimethicone deposits itself preferentially on the hair fibre, in the more damaged regions. ^{(2, 17)}

• Application of a Protective Film

Once applied, amodimethicone distributes evenly over the hair surface, creating a thin, flexible silicone layer that smooths the cuticle. It crosslinks with surrounding amodimethicone molecules, establishing a resilient coating. ^{(4, 19)} This mechanism is what contributes to decreased friction and mechanical damage between the hair strands, improving detangling and shine due to a smoother light reflection. It also decreases penetration of moisture which causes frizz. ^(4,18)

• Self-limiting Deposition

As amodimethicone molecules carry a positive charge, they repel each other once deposited onto the hair shaft ⁽¹⁷⁾, stopping a thick or dense layer building up. This leads to long-lasting deep conditioning without the heavy residue, which can feel heavy for some hair types, particularly in comparison to certain conventional silicones. ^(17,19)

How Does This Improve the Hair?

The benefits of amodimethicone’s behaviour can be applied to hair care in various ways.

• Cuticle Care

It smooths the cuticles by settling in the microscopic spaces along damaged cuticle surfaces. This decreases roughness and creates a softer and smoother hair texture. ⁽¹⁸⁾ The smoother cuticles increase shine by reflecting light more evenly. ^{(4, 18,20,21)}

• Less Breakage and Heat/Colour Damage

Due to amodimethicone creating a protective silicone film, the likelihood of mechanical damage occurring decreases, by reducing friction between the hairs during brushing or styling. Additionally, the protective layer can minimise hair colouring from fading and decrease heat damage due to styling tools. ^{(2, 4, 15, 18, 20)}

• Regulating frizz

Amodimethicone establishes a hydrophobic barrier, which restricts the absorption of water from humid environments. This mechanism can help to minimise frizz and swelling of the hair. ^{(15, 18,19, 20)}

Summary

Amodimethicone has chemical properties which makes it a valuable silicone in conditioning and hair care products. Due to its amine-functionalised structure, it becomes positively charged when formulated into conditioners, creating electrostatic attraction to the negative charges on damaged hair fibres. This makes it possible for it to deposit specifically on damaged areas, creating a thin layer of defence against heat, mechanical and external damage. Regarding application and functionality, this allows for smoother cuticles, better detangling and frizz control, and the appearance of shinier, healthier hair.

References

1.  Amlagreen.com. (2026). Available at: https://amlagreen.com/cdn/shop/articles/AdobeStock_67366201_1ea5f423-61dc-4f06-8403-b4b8c1e88e0d.jpeg?v=1593536959&width=1400.

2. Raquel, Melo, D.F., Awatef Kelati and Tosti, A. (2025). With or Without Silicones? A Comprehensive Review of Their Role in Hair Care. Skin Appendage Disorders, pp.1–6. doi:https://doi.org/10.1159/000546651.

3. FéronP. (2016). Absorption-based post-combustion capture of carbon dioxide. Oxford: Woodhead Publishing.

4. Nanjing SiSiB Silicones Co., Ltd. (2020). Fuctional Silicone - Nanjing SiSiB Silicones Co., Ltd. [online] Available at: https://www.sinosil.com/fuctional-silicone.html

5. Googleapis.com. (2026). Available at: https://patentimages.storage.googleapis.com/1d/09/41/70ab72abb705cc/pat00003.png.

6. Weiand, E., Rodriguez-Ropero, F., Roiter, Y., Angioletti-Uberti, S., Dini, D. and Ewen, J.P. (2025). Understanding and controlling the friction of human hair. Advances in colloid and interface science, [online] 345, p.103580. doi:https://doi.org/10.1016/j.cis.2025.103580.

7. Biology Insights. (2025). What Is the Cortex of Hair and What Are Its Functions? [online] Available at: https://biologyinsights.com/what-is-the-cortex-of-hair-and-what-are-its-functions/.

8. Baltenneck, F., Genty, G., Elias Bou Samra, Richena, M., Harland, D.P., Clerens, S., Leccia, E., Mickael Le Balch, Doucet, J., Michelet, J.-F. and Commo, S. (2022). Age-associated thin hair displays molecular, structural and mechanical characteristic changes. Journal of Structural Biology, 214(4), pp.107908–107908. doi:https://doi.org/10.1016/j.jsb.2022.107908.

9.  TRICHOLOGY, S. (2014). SIMONE TRICHOLOGY. [online] SIMONE TRICHOLOGY. Available at: https://www.simonehair.com/trichology-for-beginners/the-hair/.

10.  Meachum, V. (2022). Breaking Down The Fundamentals of Hair Bonds. [online] The Mestiza Muse. Available at: https://themestizamuse.com/breaking-down-the-fundamentals-of-hair-bonds/.‌

11.  Lima, C.R.R. de C., Couto, R.A.A. de, Freire, T.B., Goshiyama, A.M., Baby, A.R., Velasco, M.V.R., Constantino, V.R.L. and Matos, J. do R. (2019). Heat‐damaged evaluation of virgin hair. Journal of Cosmetic Dermatology, 18(6), pp.1885–1892. doi:https://doi.org/10.1111/jocd.12892.

12. Robbins CR. Bleaching and Oxidation of Human Hair. Chemical and Physical Behavior of Human Hair, 4th edn. Berlin, Germany: Springer - Verlag; 2012: 263-328.

13. JEONG, M.-S., LEE, C.-M., JEONG, W.-J., KIM, S.-J. and LEE, K.-Y. (2010). Significant damage of the skin and hair following hair bleaching. The Journal of Dermatology, 37(10), pp.882–887. doi:https://doi.org/10.1111/j.1346-8138.2010.00916.x.

14. Sebetić, K., Sjerobabski Masnec, I., Cavka, V., Biljan, D. and Krolo, I. (2008). UV damage of the hair. Collegium Antropologicum, [online] 32 Suppl 2, pp.163–165. Available at: https://pubmed.ncbi.nlm.nih.gov/19138021/.

15. Tate ML, Kamath YK, Ruetsch SB, Weigmann HD. Quantification and prevention of hair damage. J Soc Cosmet Chem. 1993; 44: 347-371.

16. Yang Y, Wen Y, Bin W, Meyers AM. Structure and mechanical behavior of human hair. Mater Sci Eng C. 2017; 73: 152-163.

17. Dussaud, A.D., Breen, P.C. and Koczo, K. (2013). Characterization of the deposition of silicone copolymers on keratin fibers by streaming potential measurements. Colloids and Surfaces A: Physicochemical and Engineering Aspects, [online] 434, pp.102–109. doi:https://doi.org/10.1016/j.colsurfa.2013.04.071.

18. Gavazzoni Dias, M.F.R. (2015). Hair cosmetics: An overview. International Journal of Trichology, [online] 7(1), p.2. doi:https://doi.org/10.4103/0974-7753.153450.

19. Lab Muffin Beauty Science. (2019). Amodimethicone: The Science of My Favourite Hair Ingredient. [online] Available at: https://labmuffin.com/amodimethicone-my-new-favourite-hair-ingredient/.

20. Zhou, Z., Xu, J., Lu, J., Li, J., Zhang, W. and Chen, K. (2025). Cationic cellulose nanocrystals enhance keratin adsorption to improve hair glossiness and thermal-photo protection. International journal of biological macromolecules, [online] 303, p.140492. doi:https://doi.org/10.1016/j.ijbiomac.2025.140492.

21. McMullen, R. and Jachowicz, J. (2004). Optical properties of hair: detailed examination of specular reflection patterns in various hair types. International Journal of Cosmetic Science, 26(4), pp.217–218. doi:https://doi.org/10.1111/j.0142-5463.2004.00223_3.x.

Assessed and Endorsed by the MedReport Medical Review Board