[C:1]1(=[O:8])[O:7][CH2:6][CH2:5][CH2:4][CH2:3][CH2:2]1.[O:9]1[CH2:14][CH2:13][O:12][CH2:11][C:10]1=[O:15].C(O)C(O)C.CCCCC(C([O-])=O)CC.CCCCC(C([O-])=O)CC.[Sn+2]>C1(C)C=CC=CC=1>[C:1]1(=[O:8])[O:7][CH2:6][CH2:5][CH2:4][CH2:3][CH2:2]1.[O:9]1[CH2:14][CH2:13][O:12][CH2:11][C:10]1=[O:15]A flame dried, 250 mL, round bottom single neck flask was charged with 57.1 g (0.50 mole) of ε-caprolactone, 51.0 grams (0.50 mole) of p-dioxanone, 3.7 mL (50 mmol) of propylene glycol (USP), and 0.12 mL (34 μmol) of a 0.33M stannous octoate solution in toluene. The flask was fitted with a flame dried mechanical stirrer. The flask was purged with nitrogen three times before venting with nitrogen. The reaction mixture was heated to 140° C. and maintained at this temperature for about 24 hours and then bath temperature was lowered to 110° C. and maintained at this temperature for 24 hours. The copolymer was dried under vacuum (0.1 mm Hg) at 80° C. for about 32 hours to remove any unreacted monomer. The copolymer had an inherent viscosity of 0.22 dL/g in HFIP at 25° C. The copolymer was a liquid at room temperature. The molar ratio of PCL/PDS was found to be 52.4/47.6 by proton NMR.
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