Tin(Ii) n-hexoxide as new initiator for the ring-opening polymerization of ε-caprolactone: Isoconversional kinetics analysis by non-isothermal dsc

Abstract

The kinetics of ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) initiated by 1.5 mol% of tin(II) n-hexoxide (Sn(OnHex)2) and tin(II) octoate/n-hexanol (Sn(Oct)2/n-HexOH) were effectively investigated by non-isothermal DSC technique. The DSC polymerization exotherms shifted to higher temperature range as heating rates increased. The polymerization rate increased with increasing heating rate for all initiating systems. The variation of activation energy (Ea) with monomer conversion was successfully investigated by Kissinger-Akahira-Sunose (KAS) isoconversional method. The values of Ea for the ROP of ε-CL with Sn(OnHex)2 and Sn(Oct)2/n-HexOH were 66.02±0.60 and 64.94±0.27 kJ/mol, respectively. From kinetics analysis, the reactivity of Sn(Oct)2/n-HexOH was slightly higher than Sn(OnHex)2 under identical condition. The catalytic performance of both initiating systems in the synthesis of poly(ε-caprolactone) (PCL) was investigated by bulk polymerization at temperatures of 140, 160 and 180oC. The synthesized Sn(OnHex)2 could produce higher number average molecular weight ( M n ) at 140 and 160oC than Sn(Oct)2/n-HexOH. The %yield values of all synthesized PCLs were higher than 70.2%. The synthesized Sn(OnHex)2 acted as effective initiator that could produce high molecular weight PCL in a short period of time.