Synthesis of semicrystalline poly(arylene ether) ketone thermoplastic resins and structural adhesives systems via amorphous ketimine intermediates. Influence of ketone/ether backbone ratio on thermal transition behavior

A systematic series of semicrystalline poly(arylene ether) ketones with varying ratios of ketone to ether in the polymer backbone were synthesized via nucleophilic aromatic substitution step polymerization. Ketimine derivation of the activated halide prior to the polymerization was achieved via aniline reactions which were catalyzed with molecular sieves. The ketimine derivative still activates the halide monomer but can be selectively removed under acidic conditions after the polymerization. The ketimine modified monomer allows one to synthesize an amorphous linear polymer at moderate (e.g. 150°C) conditions and to thus characterize molecular and macromolecular structure via classical means. Further studies have demonstrated that it is possible to essentially quantitatively hydrolyze the ketimine to regenerate the semicrystalline poly(arylene ether ketone), even with aqueous hydrochloric acid. The resulting material can be treated with water, dried, and characterized. With same procedures, potentially important fine (1 micron) semicrystalline powders can be achieved. The thermal and mechanical properties of these polymers have been studied as a function of the ratio of ketone to ether in the repeat unit and several important trends have been noted. The glass temperature (T_g), the crystal melting point (T_m), and even the room temperature tensile modulus appears to increase with the ketone to ether ratio.