Synthesis of thermally cross-linkable fluorine-containing poly(aryl ether ketone)s I. Phenylethynyl terminated poly(aryl ether ketone)s

Fluorine-containing poly(aryl ether ketone)s (PEKs) derived from 2,3,4,5,6-pentafluorobenzoic acid (PFBA) exhibit outstanding solubility, thermal stability, low dielectric constant, low moisture absorption and high transparency. Hence, they are expected to be available for optical and electric materials. In such applications, excellent solubility is of great advantage for making thin film and coating. Contrary to this advantage, this is of disadvantage from a point of solvent resistance. Thermally cross-linkable fluorine-containing PEKs terminated with phenylethynyl moiety (PEK-PEP) are synthesized to improve the solvent resistance in this study. Cross-linking reaction occurs over 320°C and it brings about not only the outstanding solvent resistance but also the increase of T_g. Relationship between the cross-linking density and T_g can be fundamentally interpreted by configurational entropy theory. Furthermore, the cured PEK-PEPs possess excellent thermal stability with the 10% weight loss temperature in the range from 544 to 598°C.