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

Abstract

Dibutyltin(IV) maleate (DBTML) was successfully used as a new initiator in the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) under solvent-free condition for the first time. The performance of DBTML in the ROP of ε-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 ε-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 ε-CL decreased with increasing DBTML concentration. The frequency factor (A) values for the ROP of ε-CL with 3.0 and 4.0 mol% of DBTML were 7.4 × 106 and 7.3 × 105 min−1, respectively. From mechanistic investigation by proton-nuclear magnetic resonance spectroscopy (1H-NMR), the ROP of ε-CL with DBTML was purposed via the coordination-insertion mechanism. From bulk polymerization, DBTML could produce poly(ε-caprolactone) (PCL) with the weight average molecular weight (Mw) and polydispersity index (PDI) in the range of 1.49 × 104–5.15 × 104 g/mol and 1.52–1.98, respectively. Graphic abstract: [Figure not available: see fulltext.]