Abstract
When commercial oligo- or poly(ethylene glycol)s and dibutyltin dimethoxide were condensed in bulk with elimination of methanol, no linear polycondensates were obtained and tin-containing macrocycles were the only reaction products. In order to improve the hydrolytic stability, stoichiometric amounts of γ-thiobutyrolactone were inserted into the macrocyclic oligoethers, so that the Sn-O bonds were transformed into Sn-S bonds. The formation of monomeric (containing one Bu 2 Sn group) macrocycles was confirmed. The tin-containing macrocyclic polyethers were used as macrocyclic initiators for the ring-expansion polymerization of e-caprolactone. The resulting macrocyclic poly(ether-ester)s were isolated in the form of telechelic A-B-A block copolymers after precipitation into methanol.
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