Molecular chain heterogeneity of the copolymer of L-lactide and -caprolactone(PLC) was investigated using the preparative temperature rising elution fractionation (TREF) technique and successive self-nucleation/annealing (SSA) thermal fractionation.Two PLC samples with -caprolactone compositions of 5 mol% and 10 mol% were prepared and fractionated by using TREF.For both samples

three fractions were collected and characterized with nuclear magnetic resonance spectroscopy (1H-NMR) and gel permeation chromatography (GPC).The 1H-NMR results showed that there exists obvious differences in the caproyl content among the fractions.It was also found

with GPC method

that for the fraction of higher elution temperature

the number average molecular weight (Mn) is higher and the distribution is narrower.The data obtained suggest that the fractionation is mainly the result of the difference of the chain tacticity.The chain heterogeneity of TREF fractions was further analyzed with SSA thermal fractionation.The first Ts to be used in the SSA method was carefully chosen in Domain II for all fractions.After SSA treatment

the appearance of multiple melting behavior for each fraction indicates that a heterogeneous intramolecular distribution of defects still exsits in the chains of fractionated sample.On the other hand

the intermolecular heterogeneity is evident in the different melting ranges of each fraction.