Effect of Cationic Polymers on Particle Deposition

Cationic polymers are the traditional conditioners for keratinous substrates, especially hair. This is because these substrates are normally negatively charged (low isoelectric point), and polycations employed, either alone or together with a conditioner, are the most predominant type. These polycationic polyelectrolytes have a 

One of the earliest polycationic polymers was polyethyleneimine (PEI), which was used as a model for studying polycation uptake by hair. This polymer was withdrawn from hair products in the 1970s (for safety reasons). Later, an important class of cellulosic polycationic polymers was introduced with the trade name Polymer JR (Amerchol corporation) and this is widely used for hair conditioning. Other synthetic polycationic polymers from Calgon corporation are Merquat 100 (based on dimethyldiallyl amine chloride) and Merquat 550 (based on acrylamide/ dimthyldiallylamine chloride). 

Clearly the above interactions will have a pronounced effect on particle deposition. In the absence of any other effects, addition of cationic polyelectrolytes can enhance particle deposition either by simple charge neutralisation or bridging between the particle and the surface. At high polyelectrolyte concentrations, when 

However, the above effects are complicated by the interaction of the polycationic polymer with surfactants in the formulation and this complicates the prediction of particle deposition. Investigations of the interactions that take place between the polycation, surfactants and other ingredients in the formulation are essential before a complete picture on particle deposition is possible. 

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