Efficiency and usability of silicone surfactants in emulsions

Synopsis The critical micelle contration (CMC) of silicone surfactants was determined to provide their optimal efficiency in emulsion systems. The lowest CMC value was found for the amphionic polysiloxane polyorganobetaine copolymer, which is undoubtedly the consequence of electrostatic repulsion preventing the aggregation of ionized molecules. Also the nonionic surfactants (polydimethyl siloxane polyethers) showed some differences: the surfactant with polyethylene oxide side chain is more effective compared to the polyethylene-polypropylene oxide side chain. The results of miscibility testing of silicone surfactants with common components of emulsions and creams confirm that not only silicone oils, but also silicone surfactants, should be considered as both explicitly hydrophobic and non lipophilic. The stability of emulsions containing silicone surfactants prepared by cold emulsification supported the incorporation of polyelectrolyte sodium carboxymethylcellulose, which increased viscosity of the continuous phase and prevented coalescence. The physical stability testing of prepared emulsions confirms that the used methods - centrifugation, particle size analysis and the observation of ageing at room (20-25 degrees C) and elevated temperature (40 degrees C) - give comparable results.