Thermally stable polymers, electronic applications

Polyimides (PI) were among the earliest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, structure variations, and ultimately products and applications. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as structural composites, eg, over a ton of polyimide film is presendy used on the NASA shutde orbiter. Work continues on these materials, including the more recent electronic applications. 

Foams have a large variety of applications. Solid foams are widely used as insulating materials. Due to the presence of air bubbles they have a low thermal conductivity. Polyurethane foams and Styrofoam are examples. Styrofoam is also used as a packing material. The light weight of polymer foams makes them attractive as filling materials to stabilize otherwise hollow structures. A natural solid foam is pumice stone. Metal foams are used in the automotive and aerospace industry as light and stable materials [567], Ceramic foams are developed for electronic applications as piezoelectric transducers and low dielectric constant substrates [568],... 

Macdonald and C.G. Willson, Poly(N alkysl o nitroamides) A new class of thermally stable photosensitive polymers, in Polymer Materials for Electronic Applications, ACS Symposium Series 184, E.D. Feit and C. Wilkins, Jr., Eds., American Chemical Society, Washington, D.C., pp. 73 82 (1982). A. Reiser, Photoreactive Polymers The Science and Technology of Resists, p. 267, John Wiley Sons, Hoboken, NJ (1989). 

Another group of thermally stable polymeric materials for electronic application includes poly(ether-imide-benzoxazolejs. Mercer and McKenzie [228] prepared the polymer by polycondensation of 2,2 -bis[2-(4-aminophenoxy)benzoxazole-6-yl] hexafluoropropane with pyromellitic, biphenyl, benzophenone etc., followed by thermal imidization of polyamic acid films. The polymers showed an onset temperature for polymer degradation in the range of 424°-456°C and glass transition temperatures in the range of 299 -337°C. 

Kovalev MK, Kalinina E, Androsov DA, Cho C. Synthesis of transparent and thermally stable polyimide-aramid nanocomposites -prospective materials for high-temperature electronic manufacture applications. Polymer 2013 54(l) 127-33. 

Fused thiophenes are rigid, thermally stable, and easily processable compounds. They are promising candidates for applications in molecular electronics. In this chapter, based on the number of thiophene units, the principal synthetic routes to fused thiophenes are addressed in three sections, namely thienothiophenes, dithienothiophenes, and thienoacenes, which have two, three, and more-than-three annulated thiophenes, respectively. Important examples of the construction of oligomers, further conjugated analogs, and polymers of these systems are given. 

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