Polymerization of l-lactide with SnCl2: A Low Toxic and Eco-friendly Catalyst

Abstract

Polymerizations of l-lactide catalyzed either by neat SnCl2 or by SnCl2 + difunctional cocatalysts were conducted in bulk at 180, 160 and 140 °C with variation of the Lac/Cat ratio and time. With neat SnCl2 poly(L-lactide) having weight average molecular weights (uncorrected Mw’s) up to 190 000 g mol−1 were obtained mainly consisting of linear chains. Addition of salicylic acid or 1,1-bisphenol yielded a higher fraction of cyclic polylactides but lower molecular weights. Furthermore, SnCl2 was compared with Bu2SnCl2 and various other metal chlorides and the best results were obtained with SnCl2. With ethyl L-lactate as initiator SnCl2-catalyzed ROPs were performed at 120 °C and the lac/initiator ratio was varied. All these experiments were conducted under conditions allowing for comparison with ROPs catalyzed with neat Sn(II)-2-ethyhexanoate. Such a comparison was also performed with ε-caprolactone as monomer.

Syntheses of polylactides by means of tin catalysts

“…Mass spectrometry was not available and thus, no information about the topology of SnCl 4 -catalyzed PLLA was published and the polymerization mechanism is still unknown (see below) In the case of SnCl 2 a recent study has elucidated that ROPs conducted in bulk >120 °C yield mixtures of cycles and linear chains having unidentified end groups. 156 A recent examination of various commercial alky-or aryl tin chlorides gave the following results. 208 Dimethyl tin dichloride and dibutyltin dichloride yielded reaction products mainly consisting of cycles, but the ratio of cyclic/linear chains was difficult to reproduce.…”

“…The MALDI the mass spectra do not display formation of cycles in close analogies to ROPs catalyzed by SnOct 2 under identical conditions. 156 With SnCl 2 side reactions occur and the control of the molar mass was less perfect. 79 Surprisingly, even cyclic dibutyltin catalysts, such as DSTL, 157 BuSnBuca, 158 or BuSnNaph 159 (see Scheme 25) which, when used as neat compounds, catalyse formation of cyclic polylactides by the REP mechanism (see part 4), also catalyse formation of linear chains, when an alcohol was added as initiator.…”

“…This journal is © The Royal Society of Chemistry 2022 metabolism), systematic exploration of their usefulness as catalysts for ROPs of lactide and ε-caprolactone was only reported quite recently. 79,156 With SnAc 2 and temperatures < 160 °C a full control of the molar mass is feasible up to a LA/In ratio of 100. The MALDI the mass spectra do not display formation of cycles in close analogies to ROPs catalyzed by SnOct 2 under identical conditions.…”

Inner filter effect between upconversion nanoparticles and Fe(ii)–1,10-phenanthroline complex for the detection of Sn(ii) and ascorbic acid (AA)

“…Excessive amounts of Sn can cause adverse effects on the human body's digestion, breathing and nervous system. [12][13][14] Therefore, it is particularly important to explore an accurate, simple and effective method to detect Sn(II)/Sn(IV). Conventional analysis methods for detecting Sn(II) is atomic absorption spectrometry, 13,14 spectral method, 15 voltammetry, 16,17 and potential method, 18,19 etc.…”

“…[12][13][14] Therefore, it is particularly important to explore an accurate, simple and effective method to detect Sn(II)/Sn(IV). Conventional analysis methods for detecting Sn(II) is atomic absorption spectrometry, 13,14 spectral method, 15 voltammetry, 16,17 and potential method, 18,19 etc. These methods cannot differentiate between samples of Sn(II) and Sn(IV).…”