Synthesis and rheological investigation on phase behaviors of semiflexibletype amorphous liquid crystalline poly(ester-imide)s

Main chain type thermotropic poly(ester-imide)s composed of N-(omega-carbox yalkylene) trimellitic imides and methylhydroquinone diacetate or hydroquin one diacetate were prepared by melt transesterification condensation. DSC a nd polarized light microscopy observation revealed that polymers made from hydroquinone diacetate showed both crystal melting and mesophase to isotrop ic phase transition but those from methylhydroquinone diacetate showed only mesophase to isotropic phase transition. The amorphous type liquid crystal line polymers showed extremely slow crystallization velocities. The mesopha se of all polymers was verified as a nematic one from the drops of moduli a nd viscosities at the isotropic to mesophase transition during cooling. For an amorphous liquid crystalline polymer the changes of dynamic rheological properties were checked around the mesophase to isotropic phase transition . Both isotropic and nematic phases succeeded in time-temperature superposi tion but biphase failed. (C) 2000 Elsevier Science Ltd. All rights reserved .