The new thermotropic liquid crystalline copoly(ester-imide)s were synthesized by a melt polymerization. The molar ratio of N-(ω-carboxyalkylene) trimellitic imide and 2,6-diacetoxynaphthalene was kept constant at 1:1, but the molar ratio of p-acetoxybenzoic acid to these two monomers was varied from 0.5:1 to 5:1.
These thermotropic liquid crystalline copoly(ester-imide)s turned out to have a low melting temperature(or solidification temperature), a wide nematic range from the melting temperature(or solidification temperature), and thermally stable until reaching 400℃.
The rheological properties of the polymers were studied by PHYSICA rheometer. Dynamic viscoelastic properties for the polymers with X=0.5 and X=1 showed no hysteresis behaviors in a temperature cycle. But, the sample with X=2 showed the hysteresis behavior in the cooling measurement. This might be caused by the formation of HBA block units in the main chain. This result was consistent with the results of WAXD patterns and SEM photographs.
The mechanical properties of thermotropic liquid crystalline copoly(ester-imide) fibers showed that the tensile strength increased with increasing draw ratio.