Polymer blends of polyethersulfone with all aromatic liquid crystalline co‐polyester

Polymer blends of polyethersulfone (PES) with an all aromatic liquid crystalline co‐polyester (LCP) were investigated. In addition, PES oligomers with the reactive functions end groups (−ONa) were added as a third component to the above blends in order to improve their properties. Flexural properties, such as modulus and strength, and dynamic viscoelastic properties, such as dynamic storage elasticity ( E ′) and loss tangent (tan δ), of the blends were measured. The morphology of blends was characterized using a differential scanning calorimeter (DSC) and a scanning electron microscope (SEM). Of the flexural properties, the modulus of PES increased almost linearly with increasing LCP content. However, strength decreased as LCP content increased to 20 wt%. In contrast, the addition of the PES oligomers had little effect on modulus, but strength was clearly improved. Regarding dynamic viscoelastic properties, the oligomer‐containing blends exhibited complex behavior. Regarding morphologies, SEM analysis revealed that the LCP was not fibrous in the core of the blend containing 40 wt% or less, but the addition of the PES oligomers made LCP fibrous even in blends with low LCP content. It was concluded that the PES oligomers with reactive functional groups acted as a compatibilizer in polymer blends of PES/LCP.