Use of Non‐isothermal DSC in Comparative Studies of Tin(II) Systems for the Ring‐Opening Polymerization of D‐lactide

Abstract

Understanding the kinetics and mechanisms of polymerization, particularly the role of a catalyst or initiator used, allows for the manipulation and control of the fabrication of new materials by the most convenient, straightforward routes. The kinetics of the bulk ring-opening polymerization (ROP) of d-lactide, a useful monomer employed to control the properties of poly(l-lactide), have been studied herein to identify a relatively quick (1 h), controlled, yet convenient route to moderately high molecular weight poly(d-lactide). Tin(II) octoate (Sn(Oct) 2), Sn(Oct) 2/n-butanol (nBuOH) and liquid tin(II) butoxide (Sn(OnBu) 2) as initiating systems were investigated by non-isothermal differential scanning calorimetry (DSC). Isoconversional methods were employed to determine the activation energy (E a) for each reaction. The results showed that liquid Sn(OnBu) 2 was a more efficient initiator than the commonly reported initiating systems of Sn(Oct) 2 and Sn(Oct) 2/nBuOH in terms of producing higher polymerization rates and polymer molecular weights. High-molecular-weight poly(d-lactide) (1.8 × 10 5 Da) with moderate dispersity (Р= 1.3) was obtained using 0.1 mol% liquid Sn(OnBu) 2 as the initiator at 120 °C. This work describes the applications of non-isothermal DSC and isoconversional methods in comparing the effectiveness of different initiators in the bulk ROP of d-lactide for the first time.