Acrylates/Beheneth-25 Methacrylate Copolymer is a sophisticated rheology modifier designed to provide exceptional clarity and suspension in surfactant-based systems. It functions as a hydrophobically modified alkali-swellable emulsion (HASE) to enhance formula stability and create luxury textures.
- INCI Name:
- Acrylates/Beheneth-25 Methacrylate Copolymer
- Chemical/Scientific Name:
- 2-Propenoic acid, 2-methyl-, polymer with ethyl 2-propenoate and alpha-(2-methyl-1-oxo-2-propenyl)-omega-(docosyloxy)poly(oxy-1,2-ethanediyl)
- Common Aliases:
- Aculyn 28, Rheomer 33, HASE Polymer
| Category: | Thickeners, Stabilizers |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Cosmetics, Personal Care, Haircare |
| Solubility: | Water (alkali-soluble) |
At a Glance: Properties & Effects
| Texture Enhancement: | |
| Formula Stability: | |
| Irritation Risk: |
Primary Benefits:
- Creates crystal-clear gel structures in aqueous systems.
- Provides excellent suspension for beads, exfoliants, or air bubbles.
- Offers a non-stringy, “short” flow profile for premium aesthetics.
- Resists viscosity loss in the presence of electrolytes and salts.
Potential Risks:
- Requires a pH adjustment (neutralization) to activate thickening properties.
- Incompatible with highly cationic (positively charged) ingredients.
Biological Action & Cosmetic Profile
This synthetic polymer operates via a dual mechanism involving both hydrodynamic thickening and associative thickening. As a HASE (Hydrophobically modified Alkali-Swellable Emulsion) polymer, the backbone consists of methacrylic acid and ethyl acrylate, which provides the swelling capability when the pH is raised. The “Beheneth-25” portion introduces long-chain hydrophobic tails that stick out from the polymer backbone. These tails associate with surfactant micelles and other hydrophobic components in the formula, creating a complex three-dimensional network that traps water and boosts viscosity.
The transition from a low-viscosity liquid to a thick gel occurs typically when the pH is adjusted above 5.5 using neutralizing agents such as Sodium Hydroxide, Triethanolamine, or Aminomethyl Propanol. Unlike traditional Carbomer thickeners, this specific copolymer is highly tolerant of surfactants. It maintains its structural integrity even in the presence of high salt concentrations, making it an ideal choice for clear shampoos and body washes where salt is often used to adjust thickness.
Sensory characteristics are significantly improved by the inclusion of the behenyl (C22) hydrophobic group. This specific chain length contributes to a smooth, lubricious skin feel during application, avoiding the “tacky” or “sticky” finish sometimes associated with other synthetic thickeners. Because the polymer particles swell rather than dissolve completely into a linear chain, they provide “shear-thinning” behavior. This means the product flows easily when squeezed or rubbed but stays thick and stable while resting in the bottle.
Broader Applications & Origins
While primarily recognized for its role in clear cleansing gels, this ingredient is increasingly utilized in sunscreens and moisturizing lotions to improve spreadability. It acts as a co-emulsifier that helps stabilize the oil-in-water interface. The polymer is synthesized through emulsion polymerization, ensuring a high degree of purity and consistent molecular weight distribution, which is critical for reproducible batch viscosity in large-scale manufacturing.
Routine Integration
Synergies:
- Anionic Surfactants: Works exceptionally well with Sodium Cocoyl Glutamate and other cleansers to build viscosity.
- Humectants: Pairs effectively with Glycerin and Panthenol without impacting clarity.
- Chelating Agents: Often combined with Disodium Edta to maintain stability in hard water environments.
Conflicts:
- Cationic Ingredients: May form insoluble complexes with high concentrations of polyquaterniums or cationic conditioners, leading to cloudiness or precipitation.
- Low pH Formulas: Ineffective in acidic environments below pH 5.0, where the polymer remains in its unswollen, liquid state.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel has evaluated acrylates copolymers as a group and concluded they are safe for use in cosmetic formulations. Because of their large molecular weight, these polymers cannot penetrate the skin barrier, resulting in a negligible risk of systemic toxicity or irritation. Studies indicate that even at high concentrations, they do not exhibit sensitizing potential. Regulatory bodies including CosIng and the SCCS permit their use globally without restrictive concentration limits, provided they meet purity standards regarding residual monomers.
Is this ingredient microplastic?
While it is a synthetic polymer, many liquid acrylates copolymers used in cosmetics are currently being reviewed under evolving ECHA (European Chemicals Agency) microplastic definitions. However, as they are typically used in a dissolved or swollen state in the final product rather than as solid particles, they often fall outside the “solid particulate” definition of microplastics in many jurisdictions.
Does it clog pores?
No. This copolymer is a large-molecule film former and thickener that stays on the surface of the skin. It has a comedogenic rating of 0, meaning it is non-acnegenic and safe for oily or breakout-prone skin types.
Why is my product containing this ingredient cloudy?
Cloudiness usually indicates an issue with the pH or an interaction with a cationic ingredient. If the pH drops below the activation threshold (usually around 5.5), the polymer will “crash” out of the solution, resulting in a loss of viscosity and a milky or opaque appearance.