Sublimation polyimides

In fact, the 4- or 3-aminophthalic anhydride (4-APA and 3-APA) gives only intractable oligomers as pointed out later.154 Interesting are the attempts of vapor-phase deposition of 4-APA, 3-APA, and 4-amino naphtlialic anhydride (4-ANA). The sublimation of 3-APA gives only a low yield of polyimide. With both 4-APA and 4-AN A no sublimation took place and oligomeric products were formed before melting.154... 

Chemical vapor deposition (CVD) is a process whereby a thin solid film is synthesized from the gaseous phase by a chemical reaction. It is this reactive process that distinguishes CVD from physical deposition processes, such as evaporation, sputtering, and sublimation.8 This process is well known and is used to generate inorganic thin films of high purity and quality as well as form polyimides by a step-polymerization process.9-11 Vapor deposition polymerization (VDP) is the method in which the chemical reaction in question is the polymerization of a reactive species generated in the gas phase by thermal (or radiative) activation. 

The absorption and fluorescence spectra of zone refined PMDA, sublimed BTDA and sublimed ODA model compounds in dioxane were obtained in order to identify the chromophores responsible for fluorescence of the polyimide films. 

The polyimide polymers were formed by an established procedure (17) involving the addition of stoichiometric quantities of benzophenone-tetracarboxylic dianhydride (sublimed) to the diamine dissolved in anhydrous dimethylacetamide. The polyamic acid solution was cast on Teflon, warmed (80° to 90°C) to drive off solvent, then gradually heated to a temperature of 180°C. The polyimide forms rapidly at 120 to 150°C. 

For these sensors, 2-nm thick Ti and 20-nm thick Au layers were deposited on 50-prn thick polyimide films by vacuum evaporation. Next, a 50 nm pentacene layer was deposited, again by vacuum sublimation. The pentacene layer was then doped p-type by exposure to a 1% solution of ferric chloride in water. 

---