When PLLA/PDLA blends are mixed at a non-equimolar ratio,
stereocomplex crystallites are formed between equal PLLA and
PDLA, but the excess component of PDLA or PLLA will be left
without participating in the stereocomplex crystallization. Then the
fraction of the blends that may form a stereocomplex (80% for
PLLA60/PDLA40 blend, 60% for PLLA70/PDLA30 blend, and 40% for
PLLA80/PDLA20 blend) is used to normalize the crystallinity of
stereocomplex crystallites of the non-equimolar PLLA/PDLA blends,
and the corresponding normalized crystallinity of stereocomplex
crystallites Xc(sc)N are given in Table 2. The Xc(sc)N is 61.9% for the
PLLA60/PDLA40 blend, 62.3% for PLLA70/PDLA30 blend, and 62.8% for
PLLA80/PDLA20 blend, respectively (Table 2). The Xc(sc)N of the non-
equimolar blends is much higher than that of PLLA50/PDLA50 blend,
which is 51.6% (Table 1). The results indicate that stereocomplex
formation is more efficient for non-equimolar blends than for the
equimolar one by the low temperature approach. Moreover, with
a deviation of weight ratio from 50:50, Tm(sc) decreases, but Tm(sc)
of PLLA80/PDLA20 blend (219.9 C) is still higher than that of PLLA50/
PDLA50 blend by conventional melt blending (218.9 C) and solu-
tion casting (213.9 C) methods.