The anisotropy of the thermal expansion of polyimide films was investigated . Out‐of‐plane or thickness direction coefficients of linear thermal expansion (CTE) were calculated from the difference between the coefficient of volumetric expansion (CVE) and the sum of the in‐plane or film direction coefficients of linear thermal expansion for commercial and spin‐coated PMDA//ODA and BPDA//PPD films and spin coated BTDA//ODA/MPD films. The CVEs were obtained from a pressure‐volume‐temperature (PVT) technique based on Bridgeman bellows. The CVE was shown to be essentially constant, independent of molecular orientation and thickness. A decrease in the in‐plane CTEs therefore occurs at the expense of an increase in the out‐of‐plane CTE. In all cases the calculated out‐of‐plane CTE was higher than the measured in‐plane CTE. The ratio of the out‐of‐plane CTE to the in‐plane CTE was 1.2, 3.8, and 49.3 for the spin‐coated BTDA//ODA/MPD, PMDA//ODA, and BPDA//PPD films, respectively. © 1994 John Wiley & Sons, Inc.

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Selective chemical reaction was employed to overcome problems related to molecular characterization of polyimides due to their insolubility. N-Methylethanolamine was used to induce ring opening, and chain cleavage was carried out by reaction with hydrazine. These reactions were used to enhance solubility of poly(trimellitic anhydride-co-4,4′-methylenedianiline), poly(pyromellitic dianhydrideco-4,4′-oxydianiline), and its amic acid form in MALDI and ESI friendly solvents, thus enabling their qualitative analysis by these techniques for the first time. Derivatives of poly(trimellitic anhydride-co-4,4′-methylenedianiline), made with 2-fluoro-1-methylpyridinium p-toluenesulfonate to introduce charge on the polymer, were used to increase ionization efficiency and intensity in positive ion MALDI spectra.

The surfaces of polyimide films and the structure just below the surfaces have been extensively studied as people have sought to improve and understand the key factors controlling adhesion. Treatments of all types from primers to plasma etching to sand blasting have been evaluated with varying efforts depending on the application. In recent years, the emphasis has been on understanding the chemical and morphological changes effected by these treatments and then correlating chemistry and morphology with adhesion. The picture that emerges is that surface energy alone, as is the case with most polymers, usually is insufficient to predict adhesion to polyimides. Instead, initial bond strength and bond durability, whether with adhesives or metals directly deposited on the film, depend on chemical bonding, diffusion between deposited layers and the polyimide, formation of a micro composite region controlled in part by topography and the viscoelastic properties of the polymer below the surface. Poor viscoelastic behavior frequently is characterized as a weak boundary layer. Recent work has shown that small amounts of organometallics that diffuse to the surface during the film forming process can significantly affect bondability both to adhesives and to vacuum deposited metals. The possible effect of these additives on bond formation, viscoelastic properties, diffusion and topography is under investigation and will be discussed along with an over view of the primary film forming steps that might affect surface chemistry and structure.