What Is C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane?
C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane is a silicone-based polymer made by linking long-chain alkyl groups (containing 26 to 28 carbon atoms) with a propyl-substituted silsesquioxane backbone. The result is a flexible, lightweight material that forms an invisible film on skin or hair. Most suppliers derive the alkyl portion from plant oils such as coconut or palm, then combine it with silica-derived silanes in a controlled hydrolysis-condensation process. This reaction takes place in closed reactors where temperature, pH and moisture levels are carefully managed to create a uniform polymer with consistent performance.
Silicone resins like this one began appearing in cosmetics in the late 1990s when formulators were searching for ingredients that could provide breathability without the greasy feel of traditional occlusives. Advances in silicone chemistry allowed manufacturers to graft longer alkyl chains onto silsesquioxanes, giving rise to C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane. Today it is found in a range of leave-on and rinse-off products including moisturizers, primers, sunscreens, hair serums, styling creams, long-wear foundations and sheet masks where a smooth, flexible film is desirable.
C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane’s Cosmetic Benefits/Uses
This ingredient is valued for the way it improves both the feel and performance of a formula.
- Film forming: Creates a breathable shield that locks in moisture, enhances spreadability and boosts the wear time of color cosmetics without feeling heavy or sticky
- Viscosity controlling: Helps fine-tune thickness so products glide on evenly and stay stable over time, reducing the chance of separation in lotions, creams and serums
Who Can Use C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane
This silicone resin sits lightly on the surface so it is generally well tolerated by all skin types including dry, oily, combination and normal skin. Sensitive skin usually fares well too because the polymer is inert and non reactive, though those who struggle with any kind of silicone sensitivity should proceed with caution.
The ingredient is synthetic and the long-chain alkyl groups are typically sourced from plant oils, not animal derivatives, so products containing it are suitable for vegans and vegetarians. If a formula also carries a vegan certification you can be confident no animal-derived processing aids were involved.
No data links this polymer to hormonal disruption or fetal risk, so pregnant or breastfeeding women can usually use it. This is not medical advice and anyone who is expecting or nursing should confirm product choices with a qualified healthcare professional first.
C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane does not make skin more sensitive to sunlight so it does not raise the risk of sunburn or require special timing of application. It can actually help keep sunscreen actives in place by forming a flexible film.
Potential Side Effects/Adverse Reactions
Reactions to topical C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane vary from person to person. The points below list potential issues, but most people will experience none of them when the ingredient is used at normal cosmetic levels.
- Mild skin irritation such as transient redness or itching, particularly on very reactive skin
- Breakouts in individuals who are highly prone to silicone-related congestion
- Allergic contact dermatitis in the rare case of a true silicone allergy
- Product build-up on hair leading to dullness or a weighed-down feel if cleansed inadequately
- Pilling when layered with incompatible water-rich formulas due to the fast-forming surface film
If any unwanted reaction occurs stop using the product and seek advice from a medical professional.
Comedogenic Rating
Rating: 1/5
This polymer sits on top of skin, forms a thin breathable film and has a large molecular size so it is unlikely to clog pores. It does not melt into sebum the way heavier oils can, giving it a low comedogenic profile. Rarely, buildup from repeated use or layering with very occlusive products could trap debris, but ordinary cleansing prevents that.
Generally suitable for acne-prone or breakout-prone skin.
Worth noting: every formula is different. If C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane is blended with highly comedogenic oils the finished product’s pore-clogging potential may rise.
Summary
C26-28 Alkyldimethylsilyl Polypropylsilsesquioxane is a silicone resin that mainly forms a flexible moisture-locking film and fine-tunes viscosity, helping products feel silky, last longer and stay stable. Its lightweight structure lets skin and hair breathe while still giving slip and spreadability, which is why formulators reach for it in primers, sunscreens, hair serums and long-wear makeup.
It is not the hottest ingredient on the market but it has a steady fan base among brands aiming for a smooth high-performance finish without greasiness.
Safety data show it is generally non-irritating, non-sensitizing and non-comedogenic for most users. As with any cosmetic ingredient it is smart to patch test a new product first, especially if you have very reactive or acne-prone skin.