Ring-opening polymerization of ε-caprolactone initiated by tin(II) octoate/n-hexanol: DSC isoconversional kinetics analysis and polymer synthesis

The kinetics of ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) initiated by 1.0, 1.5 and 2.0 mol% of stannous(II) octoate/n-hexanol (Sn(Oct)2/n-HexOH) wase successfully studied by non-isothermal differential scanning calorimetry (DSC) at heating rates of 5, 10, 15 and 20 °C/min. The DSC polymerization kinetic parameters of ε-CL were calculated using differential (Friedman) and integral isoconversional methods (Kissinger-Akahira-Sunose, KAS). The average activation energy (Ea) values obtained from Friedman and KAS methods were in the range of 64.9–70.5 kJ/mol and 64.9–80.4 kJ/mol, respectively. The values of frequency factor (A) were determined from model fitting method using Avrami-Erofeev reaction model. The average values of A for the ROP of ε-CL initiated by 1.0, 1.5 and 2.0 mol% of Sn(Oct)2/n-HexOH (1:2) were 7.3x107, 2.8x106 and 1.2x106 min−1, respectively. From kinetics studied, the polymerization rate of ε-CL increased with increasing initiator concentration. The performance of Sn(Oct)2/n-HexOH in the synthesis of poly(ε-caprolactone) (PCL) was investigated by bulk polymerization at temperatures of 140, 160 and 180 °C. Sn(Oct)2/n-HexOH (1:2) could produce high number average molecular weight ($$\overline {{M_{\rm{n}}}}$$= 9.0 × 104 g/mol) and %yield (89%) of PCL in a short period of time at Sn(Oct)2 concentration of 0.1 mol% and temperature of 160°C. The mechanism of the ROP of ε-CL with Sn(Oct)2/n-HexOH was proposed through the coordination-insertion mechanism

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

Understanding the kinetics and mechanism of polymerization, particularly the role of the 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 (Ea) 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 (1.8×105 Da) with moderate dispersity (Ð 1.3) was obtained using 0.1 mol% liquid Sn(OnBu)2 as the initiator at 120 °C. This present 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

Organocatalytic Ring-Opening Polymerization of ε-Caprolactone Using bis(N-(N′-butylimidazolium)alkane Dicationic Ionic Liquids as the Metal-Free Catalysts: Polymer Synthesis, Kinetics and DFT Mechanistic Study

In this work, we successfully synthesized high thermal stable 1,n-bis(N-(N′-butylimidazolium)alkane bishexafluorophosphates (1,n-bis[Bim][PF6], n = 4, 6, 8, and 10) catalysts in 55–70% yields from imidazole which were applied as non-toxic DILs catalysts with 1-butanol as initiator for the bulk ROP of ε-caprolactone (CL) in the varied ratio of CL/nBuOH/1,4-bis[Bim][PF6] from 200/1.0/0.25–4.0 to 700/1.0/0.25–4.0 by mol%. The result found that the optimal ratio of CL/nBuOH/1,4-bis[Bim][PF6] 400/1.0/0.5 mol% at 120 °C for 72 h led to the polymerization conversions higher than 95%, with the molecular weight (Mw) of PCL 20,130 g mol−1 (Đ~1.80). The polymerization rate of CL increased with the decreasing linker chain length of ionic liquids. Moreover, the mechanistic study was investigated by DFT using B3LYP (6–31G(d,p)) as basis set. The most plausible mechanism included the stepwise and coordination insertion in which the alkoxide insertion step is the rate-determining step