Stereocomplexation and morphology of enantiomeric poly(lactic acid)s with moderate-molecular-weight

The thermal behavior and spherulitic morphologies Of poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) 1/1 blend with weight-molecular-weight of 105 order, together with those of pure PLLA and PDLA, were investigated using differential scanning calorimetry and polarized optical microscopy. It was found that in the blend, stereocomplex crystallites could be formed exclusively or coexisted with homocrystallites depending on thermal history. Banded to nonbanded spherulitic. morphological transition occurred for melt-crystallized PLLA and PDLA, while the blend presented exclusively nonbanded spherulitic morphologies in the temperature range investigated. The spherulite growth of the blend occurred within a wider temperature range (<= 180 degrees C) compared with that of homopolymers (< 150 degrees C), while the spherulite growth rates were comparable for both the blend and homopolymers. (c) 2007 Wiley Periodicals, Inc.