Synthesis of poly(lactide) blends by Melt/Solid polycondensation

Different blend compositions of amorphous poly(D,L-lactic acid) (PDLLA) and crystalline poly(L-lactic acid) (PLLA) of various molecular weights are prepared in one step by melt/solid polycondensation in the presence of different concentrations of either SnCl2 center dot 2H(2)O/p-toluene sulfonic acid (PTSA) 1:1 or Sb2O3 as a catalyst. The prepared blends are characterized using differential scanning calorimeter (DSC) and gel permeation chromatography (GPC). The results confirm that using a monomer source in the form of a non-racemic D,L-lactic acid mixture leads to PIA containing both amorphous (DL-based) PIA and crystalline (L-based) PIA. In addition, the polymers prepared in the presence of Sb2O3 as a catalyst acquire higher molecular weights (two- or three-fold) with respect to the comparable polymers prepared from a pure L-lactic acid source. The molecular weight measurements of the samples after exposure to degradation medium (phosphate buffer pH 7.4 at 37 degrees C) prove that the degradation occurs preferentially in the amorphous part.