SYNTHESIS AND PROPERTIES OF POLY(ETHER ETHER KETONE KETONE)-POLY(ETHER SULFONE) BLOCK-COPOLYMERS

Poly(ether ether ketone ketone)-poly(ether sulfone) (PEEKK/PES) block copolymers were prepared from the corresponding oligomers via a nucleo philic aromatic substitution reaction, and the <(M)over bar(n)> of the PEEKK segment was fixed at 12,000, while the <(M)over bar(n)>'s of th e PES segment ranged from 250 to 12,680. The different properties of t he copolymers were investigated by differential scanning calorimetry ( DSC), wide-angle X-ray diffraction (WAXD), ther mogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The results showed that the relationship between T-g and compositions of copolymers approxima tely followed the formula 1/T-g = W-1/T-g1 + W-2/T-g2. The PES content and the segment length of the copolymers had a significant influence on their melting points and crystallization behavior. The thermal prop erties and dynamic mechanical behavior of the copolymers were also stu died. In the study of isothermal crystallization, the copolymers have the same nucleation mechanism and crystal growth as that of pure PEEKK . Owing to the introduction of the PES segment into the PEEKK main cha in, it increases the free energy which forms the critical crystal nucl eus and produces a resistant action to the whole crystallization proce ss of the PEEKK segment. (C) 1996 John Wiley & Sons,Inc.