| 초록 |
The ring-opening polymerization of L-Lactide (L-LA) initiated with 1-dodecanol/Sn(Oct)2 system was carried out in supercritical chlorodifluoromethane (scR22) at 110 ℃, under a pressure of 200-205 bar. 1H NMR study suggested that polymerization proceeded via a traditional coordination insertion mechanism involving tin alkoxide bond and cleavage of acyl-oxygen bond of the monomer. The polymerization is controlled as assessed by the linear relation dependence of ln([LA]0/[LA]) on polymerization time and Mn,GPC on conversion. The relative polymerization rate constants increase with increasing Sn(Oct)2 concentration and 1-dodecanol concentration, respectively. GPC analysis indicates the molecular weight distribution is bimodal, at least at certain conversion. The mechanisms of the initiation and propagation steps in scR22 are proposed. |
