尾链数目对聚苯乙烯类高分子相行为和相结构的影响

series of polystyrenes with the different number of alkyl tails (PS-m) were synthesized via conventional free radical polymerization. The chemical structures of the monomers were confirmed by 1H NMR, 13C NMR and Mass Spectrometry. The corresponding polymers were performed with 1H NMR, gel permeation chromatography and thermos-gravimetric analysis. The phase behaviors of the polymers were investigated by the combination of techniques including differential scanning calorimetry, polarizing optical microscope , 1D and 2D wide-angle X-ray diffraction, respectively. The results showed that the number of alkyl tails has significant effects on the phase structure and phase transition for the polystyrenes. When m = 1 and 2, PS-1 and PS-2 was amorphous above the melting point. However, for PS-3, above the melting point, the polymer was the amorphous firstly, when the temperature rose to about 240℃, PS-3 formed a columnar nematic phase structure. On the subsequent cooling, the LC phase disappeared, indicated PS-3 shows a reentrant isotropic phase during the heating process.