Cyclic polyesters .6. Preparation and characterization of two series of cyclic oligomers from solution ring-chain reactions of poly(ethylene terephthalate)

Solution ring-chain reactions of poly(ethylene terephthalate) (PET) were carried out using a high boiling solvent, 1-methyl naphthalene and catalyst. At a dilution of 1/10 (w/w polymer/solvent) and catalyst concentration of 0.5% (w/w), a reaction with tetraisopropyl orthotitanate, gave cyclics at a yield of 3 wt%, with dibutyltin bis (2-ethyl-hexanoate) the yield was ii wt%, and with zinc acetate it was 20 wt%. Increasing the dilution of the reaction to 1/30 (w/w polymer/solvent) using zinc acetate as catalyst, increased the yield of the cyclics to 30 wt%. The cyclics were analysed using PL-gel mixed-E gel permeation chromatographic columns, and by H-1 nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectrometry, and liquid chromatography tandem mass spectrometry. The cyclic compounds (CO.C6K4.CO.O.CH2.CH2.O)(x), where x = 3-13, 30-130 skeletal bonds), were identified together with a series of ring compounds (CO.C6H4.CO.O.CH2.CK2.O)(x)CH2.CH2.O, (where x = 2-7) which were also found to be present. This latter series has not been previously reported. (C) 1997 Elsevier Science Ltd.