Effects of Molecular Architecture on the Stereocomplex Crystallization in Poly(lactic acid) Blends.

The crystallization behavior of two chemically identical but physically different co-crystallizing poly( l-lactic acid) (PLLA)-based blends is studied. The first set studied involves an all- l unit polymer (PLLA) co-crystallizing with a PDLA-miscible soft polyether-PDLA triblock copoly­mer, where d refers to the d isomer. The second set studied involves homopolymer blends of PLLA/miscible soft polyether/PDLA with compositions identical to the first set. Crystallization is performed under isothermal and non-isothermal crystallization conditions and the crystallization kinetics, crystal perfection, and the blend morphology are investigated. It is clear that the stereocomplex crystallization is significantly slower in the triblock copolymer blends in comparison with the homopolymer blends. Furthermore, based on diffraction, spectroscopic, and thermal data, it is found that the stereocomplex crystals formed in the homopolymer blends achieve higher order and perfection, with a melting temperature 15-20 °C higher than those formed in the triblock blends. [ABSTRACT FROM AUTHOR]