A series of polycaprolactone-b-poly(ethylene glycol) (PCL-b-PEG) and star-branched polycaprolactone (SPCL) polymers were successfully synthesized by ring-opening polymerization method

and the resulting polymer were characterized using 1H-NMR.The results of GPC indicate that the copolymers and star-branched polymers have low polydispersity index and their molecular weight is accordance with the 1H-NMR results.Phase separation method was used to prepare self-assembling aggregates of PCL-b-PEG with SPCL and without SPCL.The self-assembling aggregates were characterized by turbidity

dynamic light scattering (DLS)

SEM and FTIR.The results of SEM and DLS proved that with the SPCL added the diameter of the self-assembling aggregates became larger than that of the aggregates without the SPCL

and the results of FTIR also proved PCL-b-PEG and SPCL could self-assemble together.The length of PEG and PCL in PCL-b-PEG is an important factor to influence the diameter of the self-assembling aggregates

and with decreasing the length of PEG or increaing the length of PCL the diameter became larger.The diameter of the self-assembling aggregates depended on the length

the number of arms and the amount of SPCL

and the diameter increased with the length and the arm number of SPCL.The results of the research may provide some information for the encapsulation of hydrophobic drugs in amphiphilic copolymers.