Synthesis of mPEG-PCL Di-block Copolymer

An mPEG-PCL di-block copolymer was synthesized by ring-opening polymerization of CL (Sigma-Aldrich) and poly (ethylene glycol) methyl ether (mPEG; M_n = 750, Sigma-Aldrich) in the presence of tin (II) 2-ethylhexanoate [Sn (Oct)₂, Sigma-Aldrich] as the catalyst [49 (link)]. Briefly, mPEG (10 mmol) and distilled CL (150 mmol) were prepared in a 3-necked round-bottom flask under a nitrogen atmosphere. The mixture was heated up to 140 °C and then allowed to react with Sn(Oct)₂ (0.2 mmol) for 1.5 h. The product was dissolved in dichloromethane and precipitated with cold diethyl ether, followed by vacuum drying for 24 h to obtain mPEG-PCL.