Infrared study on the crystallization behavior and prestructural change of syndiotactic polystyrene in its blends with small amounts of poly(2,6-dimethyl-1,4-phenylene ether)

Fourier transform infrared spectra were measured for syndiotactic polystyrene (SPS) and its miscible blends with poly(2,6-dimethyl-1,4-phenylene ether) (PPE) of 3, 7, and 10 wt % over a temperature range of 303-493 K at an increment of 10 K. Crystallization of SPS from the glass state to the planar all-trans form occurred in the temperature range of 423-453 K and was delayed by about 10 K in the SPS/PPE blends, as evidenced by the temperature-dependent absorbance changes in bands at 2846.7, 1374.0, 1333.5, 1222.7, 1091.3, 964.1, 939.2, and 839.8 cm(-1). A downward shift of the CH2 symmetric stretching band during the heat-induced crystallization was observed. A kind of "prestructural change" from 383 to 423 K was identified for pure SPS by the temperature-dependent changes in the combination modes of aryl CH out-of-plane deformation vibrations. It was diminished in the SPS/PPE blends with the increase in the PPE content, and disappeared in the blends of 10 wt % PPE. This phenomenon was explained by the favorable dispersive interaction between the phenyl rings of SPS and PPE, which was responsible for the blend compatibility.