Polymers – Cosmetic Uses in Skin Care and Formulation

What Are Polymers?

Polymers are large molecules composed of repeating structural units. In cosmetic formulations, polymeric materials can interact with both skin proteins and skin lipids, influencing how an ingredient deposits on and remains on the skin surface.

The interaction between polymers and the skin depends on several important characteristics.

Factors Affecting Polymer–Skin Interaction

Positive Charge Density

The more cationic a polymer is, the stronger its potential interaction with the negatively charged surface of the skin. This can improve the polymer's ability to deposit on the skin.

Hydrophobicity

The presence of hydrophobic groups on the polymer backbone can promote van der Waals interactions with hydrophobic regions of keratin. This can contribute to adhesion and deposition on the skin surface.

Molecular Weight

Molecular weight has an important influence on polymer substantivity. Generally, higher-molecular-weight polymers have greater substantivity and stronger film-forming properties.

Very low-molecular-weight polymers, however, can more easily enter surface irregularities and adsorb into the superficial stratum corneum.

Interaction with Surfactants

The surfactants present in a finished cosmetic product can influence polymer deposition. Polymers may interact with surfactants through electrostatic or hydrophobic interactions.

Competition between polymers and surfactants for anchoring sites on the skin can also occur. This may reduce the adsorption and deposition of the polymer on the skin surface.

Cosmetic Applications

Because of these properties, polymers are important functional ingredients in many cosmetic formulations. Their ability to form films and interact with the skin can be used to influence product feel, substantivity, conditioning, and skin deposition.

References

Handbook of Cosmetic Science and Technology – André O. Barel, Marc Paye, Howard I. Maibach.