Preparation of Polymeric Micelles Consisting of Poly(propylene glycol) and Poly(caprolactone)

Abstract

The ring-opening polymerization of epsilon-caprolactone (CL) was carried out with polypropylene glycol (PPG) as an initiator in the presence of the monomer activator HCl center dot Et2O to synthesize poly(epsilon-caprolactone) poly(propyleneglycol) Poly(epsilon-caprolactone) (PCL-PPG-PCL) triblock copolymers with change of length PPG and PCL. The micelle formation of PCL PPG PCL triblock copolymers in an aqueous phase was confirmed by NMR, dynamic light scattering and fluorescence techniques. The critical micelle concentration (CMC) of the PCL PPG PCL triblock copolymers, determined from fluorescence measurements, was in range of 1.4 x 10(-3)-4.6 x 10(-3) mg/ml with dependence on block lengths of PPG and PCL. The partition equilibrium constant, K-v, which is an indicator of the hydrophobicity of the micelles of the PCL PPG PCL triblock copolymers in aqueous media, was also changed with dependence on length PPG and PCL. We confirmed that the PCL PPG PCL triblock copolymers formed micelles and hence may be potential hydrophobic drug carriers.