Plasticization of semicrystalline poly(L-lactide) (PLA) with a new plasticizer - poly(propylene glycol) (PPG) is described. PLA was plasticized with PPG with nominal M, of 425 g/mol (PPG4) and 1000 g/mol (PPG1) and crystallized. The plasticization decreased T-g, which was reflected in a lower yield stress and improved elongation at break. The crystallization in the blends was accompanied by a phase separation facilitated by an increase of plasticizer concentration in the amorphous phase and by annealing of blends at crystallization temperature. The ultimate properties of the blends with high plasticizer contents correlated with the acceleration of spherulite growth rate that reflected accumulation of plasticizer in front of growing spherulites causing weakness of interspherulitic boundaries. In PLA/PPG1 blends the phase separation was the most intense and led to the formation of PPGI droplets, which facilitated plastic deformation of the blends and enabled to achieve the elongation at break of about 90-100% for 10 and 12.5 wt% PPGI content in spite of relatively high T, of PLA rich phase of the respective blends, 46.1-47.6 degrees C. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal M, of 600 g/mol, was also used to plasticize PLA for comparison. (c) 2006 Elsevier Ltd. All rights reserved.