This thesis has focused on the synthesis and characterization of amino functional monomers, principally monomers containing aryl phosphine oxide units. Utilization of these monomers was demonstrated in various types of linear and network polymerizations. The diamines monomers included bis(3-aminophenyl) methyl phosphine oxide (DAMPO), bis(3-aminophenyl) phenyl phosphine oxide (DAPPO), bis(3-aminophenoxy phenyl) phenyl phosphine oxide (BAPPO) and bis(3-aminophenoxy phenyl) methyl Phosphine oxide (BAMPO). From these monomers high molecular weight poly(ether imides), polyurea-urethanes, poly(arylene ether ketones) poly(arylene ether sulfones) and poly(arylene ether phosphine oxides) were. Internal and external fire testing methodologies showed that the new polymers containing phosphine oxide units were fire resistant while maintaining the desirable physical characteristics of carefully selected control systems. In addition, suitable curing schedules for epoxy networks were determined by using dielectric monitoring techniques. The curing rates varied with the structure of the monomers and were slowest for the deactivated control (4,4'aminophenyl sulfone). Epoxy networks containing aryl phosphine oxide units had higher char yields in dynamic thermogravimetric analyses than control specimens. This correlated with their superior flame resistance. The brittle epoxy matrices were subsequently modified with reactive or non-reactive thermoplastic polymers in order to improve their fracture toughness. Poly(ether imides) and poly(ether sulfones) showed good phase separation behavior with tetrafunctional epoxy matrices during the curing reactions, as confirmed by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). Mechanical tests showed that reactive thermoplastic modification of the epoxy networks improved the fracture toughness of the systems, without noticeable decreases in other characteristics such as flexural modulus. Reactive systems also maintained chemical resistance in contrast to non-reactive thermoplastic controls. / Ph. D.