Polymerization of e-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:  Bu[O(O)C(CH2)5]nOSnOct, Bu[O(O)C(CH2)5]nOct, Bu[O(O)C(CH2)5]nOH, H[O(O)C(CH2)5]nOct, H[O(O)C(CH2)5]nOH, macrocyclics [O(O)C(CH2)5]n, 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 resul...

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

The kinetics and mechanism of l,l-dilactide (LA) polymerization, initiated with tin(II) butoxide (Sn(OBu)2) and carried out in THF solvent (from 20 to 80 °C) or in bulk (at 120 °C), were studied. Polarimetric and size exclusion chromatography (SEC) measurements showed that initiation was fast and quantitative; termination and intramolecular transesterification (backbiting) were not observed. According to the 1H NMR and MALDI-TOF spectra analysis, both alkoxide groups in Sn(OBu)2 were converted into poly(l-lactide) (PLA) growing chains, and monomer addition proceeded with the acyl−oxygen bond scission. SEC and osmometric measurements revealed that number-average molar masses (Mn) of PLA chains were equal to the ratio 144.13([LA]0 − [LA])/2[Sn(OBu)2]0 in the range of Mn from 103 up to ≈106. Propagation was first order (internally) in LA; it was also approximately first order in initiator (at least for [Sn(OBu)2]0 > 10-3 mol L-1). The rate constant of propagation (kp, for one macroalkoxide chain) was equal t...

Polymerization of l,l-Dilactide Initiated by Tin(II) Butoxide

Characterization of star-shaped poly(l-lactide)s by liquid chromatography at critical conditions

Resorbable and highly elastic block copolymers from 1,5-dioxepan-2-one and L-lactide with controlled tensile properties and hydrophilicity.

l-Lactide macromonomers with an incorporated double bond were successfully synthesized by controlled ring-opening polymerization initiated by two new cyclic tin alkoxides (1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene and 9,9,20,20-tetrabutyl-8,10,19,21-tetraoxa-9,20-distanna-dispiro[5.5.5.5]docosa-2,14-diene). Initiators and crude reaction mixtures were characterized by NMR. 1H NMR analysis showed that the initiators were completely reacted in the polymerization and that both tin−oxygen bonds were reactive and participated in propagation. The polymerizations were performed in chloroform at 60 °C, and the molecular weight was effectively controlled by adjusting the monomer-to-initiator ratio. The molecular weight distribution was narrow (<1.1) for both high and low molecular weights (3000−72 000 g/mol). A plot of Mn vs conversion was linear up to a conversion of 98%, showing a system propagating in a controlled manner. The kinetic investigation showed that all of the polymerizations were first order in m...

L-Lactide macromonomer synthesis initiated by new cyclic tin alkoxides functionalized for brushlike structures

Synthesis and spectroscopic properties of tin(II) alkoxides

N-substituted derivatives of 5-aza-2,8-dioxa-1-stannocyclooctane, which is a heterocyclic compound of tin(II), have been synthesized in high yields by transesterification of dimethoxy- or di-n-butoxytin(II) with di-ethanolamines. All the compounds are monomers in the vapor phase and the soluble species are associated to some degree in chloroform solution.

Ray Gsell

Papers

Synthesis and spectroscopic properties of tin(II) alkoxides

Synthesis of 5-AZA-2,8-Dioxa-1-Stannocyclooctane and N-Organo Substituted Derivatives

Spectroscopic properties of 5-aza-2,8-dioxa-1-stannocyclooctanes