Polyquaternium-31 is a high-molecular-weight, water-soluble cationic polymer designed to deliver film-forming, conditioning, and substantivity-enhancing performance in personal care products. Its quaternary ammonium groups impart a positive charge, enabling selective adsorption onto negatively charged substrates such as keratinized hair fibers and skin proteins. In skincare formulations, Polyquaternium-31 forms a thin, continuous surface film that improves tactile smoothness, reduces moisture evaporation, and enhances the sensorial profile of emulsions and cleansing systems. Although it does not act as a humectant or biologically active agent, its film-forming behavior supports barrier comfort and contributes to perceived softness and slip.

In haircare applications, Polyquaternium-31 functions as a conditioning and anti-static polymer with strong affinity for damaged or porous regions of the hair cuticle. Once deposited, it reduces inter-fiber friction, improves wet and dry combability, and minimizes flyaway without imparting excessive weight. Compared with lower-charge cationic polymers, Polyquaternium-31 offers durable conditioning with controlled buildup, making it suitable for both rinse-off and leave-on formats. It is also compatible with a broad range of surfactant systems, where it can improve foam quality and enhance deposition of other conditioning agents.