Fully imidized, high molecular weight polyimide homopolymers and random segmented poly(siloxane imide) and poly(aryl ether imide) copolymers were prepared for use as environmentally stable, tough structural matrix resins, structural adhesives, and dielectric materials. Although polyimides are well suited for such high performance engineering applications due to their excellent thermal and mechanical properties, their typical intractability in the fully imidized state has been a serious limitation. Therefore, this research has specifically focused upon several methods by which the processability of polyimide systems may be improved. One method involved the utilization of a solution imidization technique in converting the poly(amic acid) intermediate to the fully cyclized polyimide. Another important method was the incorporation of a monofunctional reagents to obtain controlled endgroups and molecular weights. Structural modifications achieved by either copolymerization with polydimethylsiloxane or polyaryl ether sulfones or ketones, or variation of the dianhydrides or diamines resulted in major strides in obtaining enhanced process ability, particularly when coupled with controlled molecular weight and the solution imidization technique. Significant reductions in the dielectric constant and water sorption, and improvements in processability were obtained by incorporating relatively nonpolar reactants, such as fluorinated dianhydrides, hydrophobic aromatic diamines, and polydimethylsiloxane oligomers. / Ph. D.

Poly(arylene ether sulfone) oligomers have been synthesized by nucleophilic aromatic substitution using potassium carbonate as base and N-methyl pyrrolidinone (NMP) as solvent. m-Aminophenol was used as an endcapper to control the molecular weight of the oligomers and to provide functional amine termination. These amine terminated oligomers can then be utilized in a variety of post reactions. Poly(arylene ether sulfone)-Polyimide segmented copolymers were synthesized using a solution imidization procedure with NMP as the solvent and o-dichlorobenzene as the azeotroping agent. The polysulfone oligomers were reacted into the system via the diamine oligomer. The segmented copolymers demonstrated good solubility characteristics, high thermal stability, and high glass transition temperatures. Previously, polyimides containing pyromellitic dianhydride (PMDA) did not remain soluble in the NMP solvent during the solution imidization, but rather precipitated out of solution when partially imidized. Incorporation of the amine terminated polysulfone oligomers into PMDA containing copolymers resulted in Systems that remained soluble even after completion of imidization. The resulting copolymers were completely soluble in many of the high boiling solvents. The copolymers demonstrated high thermal Stability and high glass transition temperatures. / Master of Science