As a part of continuous study to search for the high performance in situ composite, this study examines the miscibility of liquid crystalline poly(ester imide) (PEsI) with poly(ether imide) (PEI) and its effect on the mechanical properties and the morphology of the blends of these polymers. Liquid crystalline polymers (LCPs) were synthesized from trimellitic anhydride and α,ω-diaminoalkane with 8, 10, 12 methylene groups. Thermal condensation of these diacids with 4,4'-diacetoxybiphenyl yielded the corresponding imides of thermotropic homopolyesters. Optical polarized micrographs show that the synthesized poly(ester imides) have the smectic structure. Partial miscibility was observed from the shift of the glass transition temperature determined by differential scanning calorimetry. Increasing concentration of the liquid crystalline PEsI in the PEI/PEsI blends shifted the glass transition temperature of the PEI phase to a lower temperature. Mechanical properties of the PEI/PEsI blends were changed with the number of methylene units in PEsI. Morphologies of the partially miscible system were found to be quite different from those of an immiscible system. Strong adhesion between the matrix (PEI) and dispersed phase (LCP) was observed, but fine fibril formation was not possible due to the absence of smectic-nematic transition.

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