SUMMARY: 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 1 H and 119 Sn NMR spectroscopy, by elemental analyses, viscosity measurements and mass spectroscopy. Furthermore, the stoichiometric insertion of c-thiobutyrolactones was studied. The tin-containing macrocyclic poly(THF)-2 000 was used as macrocyclic initiator for the polymerization of e-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 -n 's) up to 50 000 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.

SUMMARY: 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 cthiobutyrolactone were inserted into the macrocyclic oligoethers, so that the Sn1O bonds were transformed into Sn1S 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.

2,2-Dibutyl-2-stanna-1,3-dioxepane (DSDOP) was polycondensed at 80 °C in bulk with succinyl chloride, adipoyl chloride, suberoyl chloride, sebacoyl chloride, and 1,12-dodecanedioyl chloride. In the case of adipoyl chloride the stoichiometry was varied and the temperature in the case of sebacoyl chloride. With a slight excess of the dicarboxylic acid chlorides, macrocyclic polyesters were obtained as the main reaction products in all cases. Depending on the dicarboxylic acid dichloride the ratio of polycondensation/cyclization steps was of the order of 20/1 to 100/1. The temperature had little influence provided that the reaction mixture remained liquid and homogeneous over the whole course of the polycondensation. Macrocyclic polyesters were also obtained as the main products when the noncyclic 1,3-bis(tributylstannoxy)butane was used as monomer. It is demonstrated that the cyclic oligo- and polyesters are not the result of transesterification and backbiting degradation processes.

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