Ternary Stereocomplex Formation of One L-Configured and Two D-Configured Optically Active Polyesters, Poly(L-2-hydroxybutanoic acid), Poly(D-2-hydroxybutanoic acid), and Poly(D-lactic acid)

The ternary stereocomplex formation of optically active polyesters, L-configured poly(L-2-hydroxybutanoic acid) [P(L-2HB)] and D-configured poly(D-2-hydroxybutanoic acid) [P(D-2HB)] and poly(D-lactic acid) (PDLA), is reported. Ternary P(L-2HB)/P(D-2HB)/PDLA blends were prepared by solution-casting to have a fixed content (50 mol %) of L-configured P(L-2HB) and different contents of D-configured P(D-2HB) relative to those of PDLA, and stereocomplex formation in the blends was investigated using wide-angle X-ray scattering and differential scanning calorimetry. The interplane distances of solution- and melt-crystallized blends were estimated from the 2 theta values at around 11 degrees and 22 degrees, and the melting temperatures of stereocomplex increased continuously with increasing the P(D-2HB) content relative to that of PDLA in the blends, indicating the formation of a ternary stereocomplex. The stereocomplex crystallinity values of ternary blends were much higher than the values calculated from binary P(L-2HB)/P(D-2HB) and P(L-2HB)/PDLA blends wherein respectively only the binary P(L-2HB)/P(D-2HB) homostereocomplex and P(L-2HB)/PDLA heterostereocomplex were formed, reflecting the facile crystallization of the ternary stereocomplex.