Rare earth (Nd

Y

La

Dy) acetates have been synthesized and used as single component catalysts for the polycondensation of dimethyl terephthalate

adipic acid and ethylene glycol first preparing aromatic/aliphatic copolyester are poly(ethylene terephthalate-co-ethylene adipate) (PETA) with high molecular weights.The copolyesters catalyzed by different rare earth acetates were characterized by means of 1H-NMR

DSC

SEC and mechanical testing.The compositions of the coplyesters calculated by the peak integrals of 1H-NMR spectra show that the molar fractions of the copolyester are consistent with the feeding molar ratio of the raw materials.The analysis on the sequence distribution of the two segments in the copolyester chains reveals that the average sequence length of PET and PEA is in the range of 1.92～2.02

and the random distribution of the two segments is also validated by the degree of randomness around 1.01. The DSC analysis shows a single glass transition temperature (Tg) of PETA at -1～-4℃ without melting temperature (Tm) suggesting the random structures and thermoplastic elastomeric property.The SEC spectra showed high weightaverage molecular weight (Mw) and polydispersities of PETA in the values of 3.24～3.88×104 g/mol and 1.81～1.94

respectively

demonstrated the high effect of the catalysts

but there is no significant difference of the activity between the four rare earth acetates.The copolyesters exhibit good mechanical properties such as high tensile strength (ca.11 MPa) and large breaking elongation (＞510%) measured with the remolten films at room temperature.The tensile strength of the copolyesters has a slight increase with the increasing of molecular weight.