Silicone oils aredesirableingredient for high quality shampoos and conditioners in hair care products. As they are insoluble in either hydrophilic or hydrophobic solvents, their common use is in the form of emulsions.Silicone oil droplets, however, have limited deposition on hair due to electrostatic repulsion with negative surface charge of hair substrates. In recent, efforts have been made to improve silicone deposition on hair substrates.

Researchers with Institute of Process Engineering (IPE) successfully prepared multilayered silicone oil droplets of narrow size distribution by combining layer-by-layer (LBL) electrostatic deposition with membrane emulsification technique.

The surface properties of multilayered droplets were characterized by surface charge and mechanical strength measurements. Silicone oil droplets were coated with large molecular weight polymers, it was found that the dispersion of coated silicone oil droplets of narrow size distribution exhibited much improved mechanical strength and increased viscosity against shear compared to uncoated droplets.

The effect of surface charge on hair deposition was investigated by adding these surface modified silicone oil droplets into the shampoos and conditioners. The results proved that the deposition of silicone oil on hair highly depends upon the surface charge, charge density of droplets and adhesive properties of coating materials.

Droplets with higher positive charge density resulted in increased deposition of silicone on hair due to electrostatic attraction. Characterization of the hair surface potential, wetting properties and friction certified the results further, showing reduced friction, decreased wetting angle and positive surface potential of high density positively charged silicone oil droplets.

Therefore, LBL surface modification combined with membrane emulsification is a promising method for preparing multilayered silicone oil droplets of increased mechanical strength, viscosity and deposition on hair.

The paper was published in Colloids and Surface B: Biointerfaces.