A series of reactive poly(aryl ether ketone) oligomers of controlled molecular weight, based on substituted hydroquinones and 4,4$\sp\prime$-difluorobenzophenone, have been synthesized and incorporated into commercial high performance epoxy-amine resin systems. The thermal and spectroscopic characteristics of the oligomers as a function of chemical structure and molecular weight have been evaluated. The oligomers are initially miscible in the epoxy-amine mixtures but are observed to phase separate during the curing process. Two phases, a thermoplastic-rich phase and a thermoset-rich phase have been identified. Four distinct morphologies; a thermoset-rich continuous phase with thermoplastic-rich inclusions, a thermoplastic-rich and thermoset-rich mixed continuous phase, a thermoplastic-rich continuous phase with thermoset-rich inclusions, and a single phase system have been observed. The morphology/property/processing relationship has been studied as a function of oligomer loading level, oligomer chemical structure, oligomer molecular weight, and curing temperature. The final thermal and mechanical properties were shown to be dependent on the phase separated morphology. Resins with thermoplastic-like toughness and thermoset-like processing characteristics have been attained when a thermoplastic-rich continuous phase is achieved. Composite and adhesive characteristics have also been measured. The synthesis and characterization of novel thermotropic liquid crystalline poly(aryl ether ketone)s is also presented. A series of copolymers based on a 4,4$\sp\prime$-biphenol mesogen and a crystal disrupting substituted hydroquinone have been synthesized. Copolymers containing between 50% and 75% biphenol were found to possess liquid crystalline characteristics. These materials are believed to be the first thermotropic liquid crystalline poly(aryl ether ketone)s reported to date.