Telechelic polyesters of ethane diol and adipic or sebacic acid by means of bismuth carboxylates as non-toxic catalysts

Dimethyladipate or dimethylsebacate were polycondensed with an excess of 1,2-ethane diol in bulk using two different temperature/time programs. Bismuth(III)n-hexanoate (BiHex3), tin(II)2-ethylhexanoate (SnOct2) and titanium tetrabutoxide were used as catalysts. Only the bismuth catalyst yielded clean telechelic polyesters having two ethylene glycol endgroups. With SnOct2 cyclic oligoesters were obtained as byproducts. Ti(OBu)4 yielded OH-terminated linear chains containing large amounts of diethylene glycol units (detectable up to three ether groups per chain). Furthermore, small amounts of cycles were also formed. Acid-catalyzed polycondensations of ethylene glycol with sebacic acid gave low yields of low oligomers, part of which contained diethylene glycol units.