Commercial poly(L-lactide) is typically heterogeneous in chain structure due to the existence of a small amount of D-lactyl units that are produced by the racemization reactions during the synthesis. In this article, the stereochemical heterogeneity of two commercial poly(L-lactide) was investigated with temperature rising elution fractionation (TREF) and successive self-nucleation/annealing (SSA) thermal fractionation. For both samples, three fractions were collected and characterized with rotatory power analysis and DSC. The fractions show distinct optical purity and DSC results, which reflect the structure differences among them directly. After SSA treatment, the observation of multiple endotherms for each physically separated fraction confirms the fractionated sample contains a heterogeneous intermolecular and intramolecular distribution of defects. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012