Synthesis, properties and crystallization behavior of poly(ether ether ketone)/poly(phenolphthalein ether sulfone) block copolymers

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Poly(ether ether ketone) (PEEK)/poly(phenolphthalein ether sulfone) (PPES) block copolymers were synthesized by a condensation reaction of fluorine‐terminated PEEK oligomers and hydroxy‐terminated PPES oligomers. The content of PPES in the copolymers was varied from 12 to 44 wt.‐%, and the effect of the compositional variation on the properties was investigated. Microphase separation was not observed and the copolymers formed a homogeneous system having good compatibility. The crystal structure of the copolymers is rhombic, equal to PEEK. The degree of crystallinity of the copolymers was low and decreased rapidly with the increase of PPES content. Concerning the cell parameters of the crystalline unit, a‐ and b‐axes are apparently longer and V is, thus, also larger compared with PEEK. Analyses of the isothermal crystallization kinetics of the copolymers provided an Avrami exponent (n) of 2.0. The glass transition temperature (Tg) of the copolymers greatly rose but the thermal stability became much poorer with the increase of PPES content. PEEK/PPES block copolymers possess good mechanical properties such as high strength and modulus.