Mechanism of Cyclic Ester Polymerization Initiated with Tin(II) Octoate. 2. Macromolecules Fitted with Tin(II) Alkoxide Species Observed Directly in MALDI−TOF Spectra

Abstract

Polymerization of -caprolactone (CL) initiated with tin(II) octoate (tin(II) 2-ethylhexanoate, (Sn(Oct)2)) in the presence of butyl alcohol (BuOH) or water and conducted in tetrahydrofuran (THF) as a solvent at 80 °C was studied using MALDI-TOF mass spectrometry. Formation of the following populations of macromolecules was revealed:and macrocyclics with incorporated tin(II) alkoxide moieties [O(O)C(CH2)5]nOSn. Thus, the most rewarding has been a direct observation of species with a tin atom covalently bonded with the polyester chain, at least for two populations of macromolecules (i.e., Bu[O(O)C(CH2)5]nOSnOct and [O(O)C( CH2)5]nOSn cyclics). Identification of the tin-containing macromolecules was based not only on the agreement between the observed m/z and the calculated molar mass values but also on the particular isotopic distribution provided by the tin atom. This result is in favor of the mechanism postulating propagation on the tin(II) alkoxide as the active center.

Ring-opening polymerization of cyclic esters in the presence of choline/SnOct2 catalytic system

“…CHOL-SnOct 2 catalytic system follows a similar reaction mechanism as alcohol-SnOct 2 system, probably [16][17][18][19][20]. It is well known that the efficiency of SnOct 2 increases when an alcohol is added as co-initiator.…”

“…During the past 20 years, the mechanism of the ring-opening polymerization of cyclic esters using the SnOct 2 has been the subject of much debate in the literature. It must be used together with a nucleophilic compound (generally an alcohol) to initiate the reaction if a controlled synthesis of the polymer is to be obtained [16][17][18][19][20].…”

Synthesis and structure-property relationships of biodegradable polyurethanes

“…The standard catalyst utilized for BioPUs based on lactide polymerization is Sn(Oct) 2 [37][38][39][40] with lauryl alcohol (1-dodecanol) which is usually added as a real initiator. The most important characteristic of Sn(Oct) 2 is that this catalyst is considered to be biologically safe [41].…”

Synthesis and Characterization of OH-Terminated Poly(trimethylene carbonate)s by Alcohol-Initiated Ring-Opening Polymerization in Melt Bulk without Using Any Catalyst

“…16,17 On the other hand, considering the catalysis mechanism of Lewis acid of such metal complexes, trifluoroacetic acid (TFA) has been also chosen as a catalyst of the ROP of seven-or six-number cyclic carbonates in order to reduce the harmfulness of metal residue.…”

“…[13][14][15] However, these metal impurities remain in these materials and would result in an unpredicted trouble in body when these resulting materials were used as biomaterials though SnOct 2 is a permitted food additive in numerous countries. 16,17 On the other hand, considering the catalysis mechanism of Lewis acid of such metal complexes, trifluoroacetic acid (TFA) has been also chosen as a catalyst of the ROP of seven-or six-number cyclic carbonates in order to reduce the harmfulness of metal residue. 18 In fact, in the absence of such catalysts, the ringopening reactions of seven-numbered cyclic carbonate also occurred.…”