Bulk ring‐opening polymerization of l‐lactide with an effective liquid tin(II) n‐butoxide initiator for biomedical applications: a comparative kinetics study

Abstract In this study, liquid tin(II) n ‐butoxide (Sn(O n Bu) 2 ) is employed as an initiator in the bulk ring‐opening polymerization of l ‐lactide. Its effectiveness is compared with the conventional tin(II) octoate/ n ‐butanol (Sn(Oct) 2 / n ‐BuOH) initiating system by analyzing kinetics parameters derived from monomer conversion data obtained through gravimetry, 1 H NMR spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Gravimetry kinetics studies of l ‐lactide ring‐opening polymerization in bulk at 120 °C for 24 h reveal that both Sn(O n Bu) 2 and Sn(Oct) 2 / n ‐BuOH achieve high conversions (>90%), with first‐order rate constants of 0.0432 and 0.0157 min −1 , respectively. These results indicate that the highly soluble liquid Sn(O n Bu) 2 leads to a faster polymerization rate and higher molecular weight ( M n = 1.45 × 10 4 g mol −1 ) than Sn(Oct) 2 / n ‐BuOH ( M n = 6.03 × 10 3 g mol −1 ). However, kinetics studies using 1 H NMR and FTIR suggest that liquid Sn(O n Bu) 2 and Sn(Oct) 2 / n ‐BuOH exhibit similar effectiveness in terms of monomer conversion. Finally, the high efficiency of liquid Sn(O n Bu) 2 is demonstrated in the first‐time synthesis of medical‐grade poly( l ‐lactide) at a large scale (500 g). This advancement paves the way for biomedical applications, such as absorbable surgical sutures, demonstrating performance comparable to commercial medical‐grade poly( l ‐lactide) products. © 2025 Society of Chemical Industry.