Doctor of Philosophy (Ph.D.)
Robert A Orwoll
Polyimides are a family of heterocyclic polymers that have received extensive evaluation as adhesives, fibers, films, moldings, composite matrices, insulators, coatings, membranes, and resists. their outstanding thermal stability, excellent mechanical and electrical properties, and chemical resistance make them attractive for many applications.;This research developed 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) developed novel diether dianhydrides for polyimide fabrication, (2) designed, characterized, and evaluated polyimide architectures based on the material application requirements, and (3) provided 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. Other favorable components of liquid crystallinity, such as flexible spacers, rigid groups, and bulky groups, were incorporated into these novel dianhydrides and polymers therefrom. 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 therefrom were synthesized to achieve lower dielectric constants. Additionally, a series of polyimide copolymers were developed for use as semi-conductor stress relief layers, 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 evaluated new and existing polyimides through physical, mechanical, and chemical means to determine possible substitutes for wire and cable insulation. These candidates 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.
© The Author
Fay, Catharine Croall, "The synthesis, characterization, and application of ether-containing polymides" (1995). Dissertations, Theses, and Masters Projects. Paper 1539623875.