Exploring effects of polymeric stabiliser molecular weight and concentration on emulsion production via stirred cell membrane emulsification

Abstract

The impact of polymer emulsifier diffusion rates and droplet formation kinetics are critical for effective control of emulsion droplet size and stability during the membrane emulsification process. It is expected that the molecular weight of a polymer stabiliser will play a significant role in the resultant emulsion due to the low energy nature of the emulsion formation mechanism and dependence on emulsifier diffusion inherent in a membrane emulsification system. Dodecane in water emulsions were formed via membrane emulsification at various concentrations and molecular weights of a polyvinyl alcohol polymer. Emulsion attributes were quantified via laser diffraction and optical microscopy over time. These data were then related to the diffusion time of polymers of different molecular weight at various concentrations via pendent droplet tensiometry. It was found that molecular weight of a polymeric stabiliser and subsequent diffusion to the interface have a significant impact on droplet size, dispersity and stability. Larger polymeric stabilisers were slower to diffuse to the interface, resulting in highly stable larger droplets, while smaller polymers quickly adsorbed to the interface but offered limited steric stabilisation and thus resulted in significant droplet coalescence. Combination of both high and low molecular weight polymers as stabilisers was observed to result in emulsions of low dispersity and controllable sizes for extremely low concentration of polymer.