Effect of Anionic Polymers on Particle Deposition

Many cosmetic formulations contain anionic polymers, mostly of the polyacrylate and polysaccharide type. The role of anionic polymers in particle deposition is complex since these polyelectrolytes interact with ions in the formulation, e.g. 

as well as with the surfactants used. Two of the most commonly used anionic polysaccharides are carboxymethylcellulose and carboxymethylchitin, obtained by carboxymethylation of cellulose and chitin, respectively. 

Several naturally occurring anionic polysaccharides exist alginic acid, pectin, carrageenans, xanthan gum, hyaluronic acidic, gum exudates (gum arabic, karaya, traganth, etc.). Cross-linking sites that occur when a polyvalent cation (e.g. Ca +) causes interpolysaccharide binding are called junction zones . 

The above complexes, which may produce colloidal particles, will greatly influence the deposition of other particles in the formulation. They may enhance binding, simply by a cooperative effect in which the polysaccharide complex interacts with the particles and increases the attraction to the surface. The pH of the whole system plays a major role since it affects the dissociation of the carboxylic groups. 

Many of the anionic polysaccharides and their complexes affect the rheology of the system and this has a pronounced effect on particle deposition. Any increase in the viscosity of the system will reduce the flux of the particles to the surface and this may reduce particle deposition. This reduction may be offset by specific interaction between the particles and the polyanion or its complex. 

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