SUMMARY E-Caprolactone was polymerized in bulk at 80°C with 2,2-dibutyl-2-stanna-l,3-dioxepane (DSDOP) as initiator. The reaction time was varied for monomer/initiator molar ratios of 20, 100 and 500. A rapid and complete conversion of the monomer and only slight transesterification or back-biting degradation were found after longer reaction times. However, significant acceleration of these side reactions was observed at 180°C. Regardless of the M7I ratios and of the reaction time the polydispersities were nearly constant. Number average molecular weights (an's) as obtained from GPC measurements are larger than the values obtained from end-group analyses by 15-25% and increase with increasing molar ratio Mn (at 100% conversion). The living character of the S n -0 "end-groups'' was demonstrated by acylation with 4-nitrobenzoyl chloride and by the synthesis of a macrocyclic block copolyester containing P-D,L-butyrolactone.

The usefulness of dimethyl-, diethyl-, dibutyl- and dioctyltin oxide for the preparation of syndiotactic poly(β-d,l-butyrolactone) was studied. Most polymerizations were conducted in bulk and a few polymerizations in toluene or chlorobenzene. The reaction temperature was varied between 50 and 100 °C. Below 50 °C the initiatiors were not reactive enough. Me2SnO proved to be the least reactive initiator. High yields and the highest molecular weights (M n's up to 80 000 and M w up to 130 000) were achieved with Bu2SnO. These high molecular weights were obtained at low monomer/initiator ratios (M/I = 50−400). In contrast to literature data, no conversion was observed at M/I ratios >600 regardless of the reaction conditions. The highest percentage of syndiotactic diads (72%) resulted either from polymerizations with Bu2SnO at 50 °C or with Et2SnO at 100 °C. Transparent films with high expansibility were cast from the 63 and 70% syndiotactic polybutyrolactone samples, which may be useful as biodegradable packaging materials.

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Using 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) as cyclic initiator the macrocyclic polymerizations of ε-caprolactone were conducted in bulk at 80 °C at monomer/initiator ratios of 20/1. The resulting tin-containing supermacrocycles were reacted in situ with an excess of isophthaloyl chloride, and this reaction mixture was polycondensed with silylated Bisphenol A at temperatures between 150 and 300 °C. The characterization of the isolated copolyesters by DSC measurements and 1H NMR and 13C NMR spectroscopy proved that they possess a perfect multiblock structure up to a reaction temperature of 240 °C. At higher temperatures transesterification causes a more or less perfect randomization of the sequence. In a second series of combined ring-opening polymerizations and ring-opening polycondensations (ROPPOC) silylated methylhydroquinone and 1,10-bis(4-chlorophenoxy)decane were used as comonomers of the macrocyclic poly(ε-caprolactone). The isolated multiblock copolyesters showed a two phasic melt with an isotropic phase containing the polylactone blocks and a nematic phase consisting of the aromatic blocks. The relationship between block lengths and phase separation is discussed.

SUMMARY: At moderate temperatures the dimeric 2,2-dibutyl-2-stanna-1,3-dioxolane (DSDOL) and the monomeric 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) add to equivalents of succinic anhydride by a clean insertion reaction into the Sn1O bonds. The resulting 30-and 17-membered macrocycles are stable up to temperatures around 115 8C and do not eliminate Bu 2 SnO in the contrast to literature reports. When succinic or glutaric acid were added to tin-containing macrocyclic poly(e-caprolactone) again no elimination of Bu 2 SnO was observed. After removal of the Bu 2 Sn groups under mild conditions telechelic poly(e-caprolactone)s with two carboxylic endgroups were isolated.