Crystallization in mixtures of optically active polyesters

Abstract

Melt-crystallized mixtures of isotactic poly(α-methyl-α-ethyl-β-propiolactone) (PMEPL) and isotactic poly(α-methyl-α-n-propyl-β-propiolactone) (PMPPL) are examined by solid-state 13 C NMR and X-ray diffraction. These techniques reveal that, in such blends, the conformation and crystal structure found for isotactic PMEPL of a given chirality depend on the configuration of the PMPPL present. In samples containing PMEPL and PMPPL of the same configuration, the two polymers crystallize independently, to give forms identical to those obtained by melt crystallization in the pure states, i.e. PMPPL crystallizes as a helix whereas PMEPL adopts a planar zigzag conformation