Abstract: Amphiphilic polymer poly(methyl methacrylate-co-methacrylic acid) [P(MMA-co-MAA)] micelles were applied to encapsulate vitamin A with dialysis method.The loaded micelles were compared with blank micelles in respect of particle size,Zeta potential and morphology.Effect of amount of vitamin A on encapsulation degree and loading extent were investigated respectively.Storage stability of the vitamin A before and after encapsulation was investigated.Meanwhile,stimulated slow releasing action of encapsulated vitamin A was studied.Results showed that critical micelle concentration of random polymer P(MMA-co-MAA) with number-averaged mole mass of 64 886 g·mol^-1 and monomer mole ratio 7∶3 in 0.1 mol·L^-1 borax buffer solution (pH=9.2) is 0.050 g·L^-1.Particle size of micelles of encapsulated vitamin A achieves nearly double of that of the blank micelles,and Zeta potential becomes more negative.When the amount of vitamin A added is 15% of the encapsulating material,the encapsulation degree and loading extent achieves 81.9% and 13.5% respectively.Under exposure of natural light,half life of vitamin A is only 15 d,while vitamin A encapsulated by P(MMA-co-MAA) micelles,still retains 56.3% after exposed to natural light for 60 d.It means that encapsulation of vitamin A with the P(MMA-co-MAA) can improve its storage stability effectively.The accumulative slow releasing of vitamin A by loaded micelles in the phosphate buffer solution (pH=5.0,which is similar to that of human skin) achieves 76.1% in 10 h.It shows that the vitamin A loaded micelles have good application prospect in cosmetics.

Key words: amphiphilic polymer micelle, vitamin A, encapsulation and release, stability