Thermal behavior and phase behavior in blends of liquid crystalline poly(aryl ether ketone) and poly(aryl ether ether ketone) containing thioether units

Thermal behavior and phase behavior in blends of liquid crystalline poly(aryl ether ketone) with lateral methoxy groups (M-PAEK) and poly(aryl ether ether ketone) containing thioether units (S-PEEK) have been investigated by differential scanning calorimetry (DSC) and polarized light microscopy (PLM) techniques. The results indicate that the composition of the blends has great effect on the phase behavior and morphology. Thin films of pure M-PAEK and S-PEEK crystallized from the melts exhibit typical mosaic and spherulitic structures, respectively. For the blends with higher M-PAEK contents (> 50%), an unusual ring-banded spherulite with structural discontinuity is formed. The bright core and rings of the ring-banded spherulites under PLM are composed of M-PAEK phase, while the dark rings consist mainly of S-PEEK phase. For the 50:50 M-PAEK/S-PEEK blend, the ring-banded spherulites and S-PEEK spherulites coexist, which implies that a partial phase separation between the two components takes place in the melting state. In S-PEEK-rich blends, a volume-filled spherulite is produced. In addition, the effect of isothermal crystallization temperature on the phase behavior, especially the ring-banded spherulite formation in the blends, is discussed.