Heating characteristics and polymerization of ε‐caprolactone under microwave irradiation

The thermal effect of microwave energy on ε‐caprolactone (CL) monomer and polymerization reaction mixture of CL with stannous octoate [Sn(Oct)2] intimately depended on the power level of microwaves and the mass scale of materials. When 10 g of CL was heated by microwaves at a power of 680 W, its temperature increased rapidly from 20 to 355°C within 5 min after which it was self‐regulated to keep constant at 360°C. Heat generation was observed when a polymerization reaction mixture of 10 g CL with 0.1% (mol/mol) Sn(Oct)2 was irradiated at 680 W. The exothermic peak was recorded at 2–5 min and its temperature was over 300°C, with the maximum at 343°C. During this period the ring‐opening polymerization of CL occurred quickly, resulting in poly(ε‐caprolactone) with weight‐average molecular weight (Mw) of 123,000 g/mol and yield of 95%.