Nanosized micelles self-assembled from amphiphilic poly(citric acid)-poly(ε-caprolactone)-poly(citric acid) copolymers

In this study, novel ABA-type amphiphilic copolymers consisting of poly(citric acid) (PCA) (A) as hydrophilic segment and poly(epsilon-caprolactone) (PCL) (B) as hydrophobic block were prepared by an approach in the following two steps: (1) ring-opening polymerization (ROP) of epsilon-caprolactone with 1,5-pentanediol initiator to obtain a hydroxyl telechelic PCL; (2) melt polycondensation reaction of hydroxyl telechelic PCL and citric acid molecules. The prepared copolymers are capable of self-assembling into nanosized micelles in aqueous solution. The influence of the copolymer composition on the micelle dimensions was investigated. The critical micellar concentration of the copolymers is in the range of 5-6.3 x 10(-2) mg/mL which is determined by the fluorescence probe technique using pyrene. Also the results indicate that CMC of self assembled micelles is influenced by the hydrophilicity of PCA-PCL-PCA copolymers depending on the CA/CP ratio, and these micelles may find great potential as drug carriers in biomedical fields.