Dibutyltin(IV) maleate as a new effective initiator for the ring-opening polymerization of ε-caprolactone: the non-isothermal kinetics, mechanism, and initiator's performance in polymer synthesis

Dibutyltin(IV) maleate (DBTML) was successfully used as a new initiator in the ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) under solvent-free condition for the first time. The performance of DBTML in the ROP of epsilon-CL was powerfully and rapidly determined by the non-isothermal differential scanning calorimetry technique. The effect of DBTML concentration on the non-isothermal ROP of epsilon-CL was studied and described. The values of activation energy (Ea) were completely determined by the peak method of Kissinger and the isoconversional method of Kissinger-Akahira-Sunose (KAS). The Ea values for the ROP of epsilon-CL decreased with increasing DBTML concentration. The frequency factor (A) values for the ROP of epsilon-CL with 3.0 and 4.0 mol% of DBTML were 7.4 x 10(6) and 7.3 x 10(5) min(-1), respectively. From mechanistic investigation by proton-nuclear magnetic resonance spectroscopy (H-1-NMR), the ROP of epsilon-CL with DBTML was purposed via the coordination-insertion mechanism. From bulk polymerization, DBTML could produce poly(epsilon-caprolactone) (PCL) with the weight average molecular weight (Mw) and polydispersity index (PDI) in the range of 1.49 x 10(4)-5.15 x 10(4) g/mol and 1.52-1.98, respectively.

Automated summary

Dibutyltin(IV) maleate (DBTML) was successfully used as a new initiator in the ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) under solvent-free conditions. The effect of DBTML concentration on the reaction was studied, and the activation energy and frequency factor were determined using different methods. Proton-nuclear magnetic resonance spectroscopy (H-1-NMR) revealed that the reaction proceeds via a coordination-insertion mechanism. In bulk polymerization, DBTML could produce poly(epsilon-caprolactone) (PCL) with specific weight average molecular weights and polydispersity indexes.