New Complex Crystals of Chiral Poly(L-lactic acid) and Different Tactic Poly(methyl methacrylate)

Based on evidence from differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and Fourier-transform infrared (FTIR) spectroscopy, a new stereocomplex crystal (DSC Tm = 175 degrees C, with WAXD 2? = 10.0 degrees and 12.5 degrees) is proven for the first time between structurally dissimilar chiral poly(L-lactic acid) (PLLA) and syndiotactic poly(methyl methacrylate) (sPMMA). There is a strong complexing capacity only between low molecular weight PLLA and sPMMA, in miscible state, at specific weight fractions (70:30). The complexing capacity is more significant when the mixtures are melt-crystallized at Tc = 110 degrees C or lower, and the intensity of this complex can be further enhanced if it is annealed between 100 and 160 degrees C, below its Tm = 175 degrees C. The new complex crystal can be formed only between PLLA and sPMMA, but not with isotactic or atactic PMMA.