Polyglycerol-poly(ε-caprolactone) block copolymer as a new semi-solid polymeric emulsifier to stabilize O/W nanoemulsions

This work introduces a new polymeric emulsifier, polyglycerol-block-poly(ε-caprolactone), to prepare and stabilize oil-in-water nanoemulsions through the formation of a semi-solid interphase between oil and water. Nanoemulsions are prepared using representative silicone and ester oils, which are widely used for commercial consumer products. The block copolymer is homogeneously solubilized in a mixture of oil and ethanol at 70 °C, and the organic solution is dispersed in water using a conventional homogenizer. Stable nanoemulsions of 220–280 nm in mean diameter are spontaneously generated. The block copolymer is reorganized at the interface to form a robust semi-solid polymeric barrier that can prevent the entrapped oil from diffusing out to the aqueous phase. The barrier exhibits excellent stability against mechanical stresses, allowing nanoemulsions to be very stable during repeated freeze/thaw cycles. This work suggests that polyglycerol-based block copolymers can be a new promising polymeric emulsifier for stabilization of nanoemulsions of various oils.