Abstract: Using the auto-oxidation and polymerization of dopamine (DA) in an alkaline solution,a polydopamine (PDA)layer was coated on the surface of the fragrance emulsion to prepare a PDA nanocapsules of fragrance.The coating property and sustained release effects of PDA on different fragrance were compared.It is found that benzyl alcohol,citronella,ethyl acetate and citronella acetate can be encapsulated inside the PDA nanocapsules,while phenyl acetaldehyde and citronellal can't be coated due to the Maillard reaction with dopamine monomer.The results of field emission scanning electron microscope (SEM)and dynamic laser light reflection (DLS)show that the fragrance nanocapsules are basically spherical and evenly distributed.The fragrance types have a great influence on the particle size,which can be changed from 88 nm (citronella acetate)to 556 nm (benzyl alcohol).The amount of fragrance encapsulated and the released behavior were investigated by both thermogravimetric analysis (TGA)and gas chromatography (GC).It is shown that the embedding rate of citronella is the highest,reaching 19.8%.After 50 days of storage at room temperature,the retention rate of the fragrance can be maintained above 69.39%,with good sustained release property.The PDA nanocapsules can provide further light screening for the photosensitizing or phototoxic fragrances owing to the ability of PDA to absorb ultraviolet and visible light.

Key words: fragrance, emulsion, nanocapsules, encapsulated, sustained release, ultraviolet screen