Thermally stable polymers, electronic

Polyimides (PI) were among the eadiest 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, stmcture variations, and ultimately products and appHcations. 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 stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

The ability to apply a planarizing, optically transparent, thermally stable polymer system that cures under relatively mild conditions has recently been demonstrated to have utility in the fabrication of multilayer devices such as advanced color liquid-crystal display31,32 The ability to apply this material as a dielectric or optical coating for thin-film electronics devices has also recently been demonstrated with the fabrication of an optical wave guiding device.33... 

Both theoretical and experimental studies show that not only are aromatic ladder polymers more thermally stable but they are also more highly conducting than analogously structured nonladder systems.In this communication, we report the synthesis and electronic properties of a ladder aromatic polymer, poly(8-methyl, 2.3-6,7-quinolino) (PMQ). The experimental procedures for preparation and characterization of PMQ are described in refs. 5 and 6. 

Other electron-withdrawing anions that enhance acidity can also improve the activity of Cr/alumina, provided that the anion is thermally stable. Sulfate is one such example [624], It can sometimes increase the polymer yield by almost 10-fold. Sulfate can be incorporated onto Cr/alumina much as fluoride can (i.e., by impregnation or dry-blending of various... 

The increasing demand for thermally stable polymers as electronic encapsulants is consistently creating a need for more information on such materials. Thermogravimetric analysis (TGA) is a valuable tool for the thermal analysis of the silicone polymers. 

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