The purpose of this research was to develop ether-containing polyimides for three applications: liquid crystalline polyimides as processing aids, polyimides for microelectronic applications, and polyimides for harsh environments. The approach consisted of three primary activities: (1) develop novel diether dianhydrides for polyimide fabrication, (2) develop, characterize, and evaluate polyimide architectures based on the material application requirements, and (3) provide extensive structure-property relationships utilizing a number of unique groups in the polymer backbone and their contributions to the resultant polymer features.

Several novel extended diether dianhydrides were synthesized. When these flexible dianhydrides were combined with rigid diamines, an alternating flexible/rigid polymer backbone resulted and hence the potential was created for liquid crystallinity. Incorporation of rigid groups such as naphthalene and biphenyl, or spacers containing -CH2- groups like butane or hexane, provided the potential to achieve liquid crystallinity in the resultant polymides. The potential liquid crystalline polyimides developed exhibited crystallinity and other desirable properties, but data were inconclusive regarding their liquid crystallinity. Extensive knowledge was gained in the synthesis of novel dianhydrides and their precursors. Additionally, structure-property relationships based on a variety of novel dianhydride moieties resulted.

High performance polymer film and coating materials are increasingly being used by the electronic circuit industry. Electrical behavior is critical for polymers used in these applications. Materials are needed with substantially lower dielectric constants. Fluorinated dianhydrides and polyimides there from were synthesized to achieve lower dielectirc constants. Additionally, a series of copolyimides was developed, using commercial and experimental monomers, for use as interlayer dielectrics and encapsulants. Several combinations were achieved that optimized mechanical, physical, and chemical properties required for the applications.

Polyimides for use in harsh environments were developed and evaluated. Two medium of particular interest were high pH to determine the polyimide's hydrolytic stability, and high-energy radiation, to determine utility of the polyimides in geosynchronous orbit. New and existing polymides were evaluated through physical, mechanical, and chemical means to determine possible substitutes for wire and cable insulators that were degrading in the presence of alkaline cleaners. These candidates also have other utility in applications requiring hydrolytic stability. Also, squaric acid containing polyimides were developed and evaluated for potential space applications. These polyimides exhibited a combination of attractive properties, especially their resistance to the radiation component of geosynchronous orbit.