It has been demonstrated that the "polycondensation" of poly(tetrahydrofuran)-diols with dibutlytin dimethoxide in bulk yields tin-containing poly(THF) macrocycles and not linear polycondensates. These macrocycles were characterized by ~1H and ~(119)Sn NMR spectroscopy, by elemental analyses, viscosity measurements and mass spectroscopy. Furthermore, the stoichiometric insertion of #gamma#-thiobutyrolactones was studied. The tin-containing macrocyclic poly(THF)-2000 was used as macrocyclic initiator for the polymerization of #epsilon#-caprolactone. The resulting macrocyclic block copoly(ether-esters) were reacted in situ with terephthaloyl chloride, succinyl chloride, or sebacoyl chloride. High temperatures proved to be advantageous for this polycondensation step. Number-average molecular weights (M-bar_n's) up to 50000 were obtained with polydispersity indices in the range of 1.6-1.7. The resulting tin-free multiblock copoly(ether-ester)s have the properties of thermoplastic elastomers and show good film-forming properties.
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