Fluorinated polyimide

Polyimides containing C—F bonds have been receiving strong attention (96—98). Fluorine-containing polyimides possess lower dielectric constant and dielectric loss because of reduced water absorption and lower electronic polarization of C—F bonds vs the corresponding C—H bonds. Fluorine-containing polyimides are often more soluble and readily processible without sacrificing thermal stabilities. The materials are appHed primarily iu... 

Often the substitution of fluorine atoms for hydrogen atoms in a polymer chain markedly increases the thermal stabiUty of the base polymer this is tme for polyimides. A typical fluorinated polyimide is prepared from the reaction of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and 2,2-bis-(4-amino phenyl)hexafluoropropane according to the following reaction (36) ... 

Polyamide or polyimide polymers are resistant to aliphatic, aromatic, and chlorinated or fluorinated hydrocarbons as well as to many acidic and basic systems but are degraded by high-temperature caustic exposures. 

The synthesis of polyimides with the pending group (aliphatic or fluorinated substituent) and some relationships between the polymeric structure and the value of the tilt angle have been reported.35... 

Figure 5.7 Fluorinated monomers used for preparation of colorless polyimides.

In addition to the research on fluorinated and cardo polyimides, an important work was devoted to the semiaromatic cycloaliphatic polyimides. Volk-sen points out the potential interest of these materials in electronic industry.64 He reports that the simplest procedure to prepare these materials is to use a cycloaliphatic dianhydride and an aromatic diamine (Fig. 5.9) instead of an aliphatic diamine and an aromatic dianhydride, which leads to formation of gels. 

Ha et al. demonstrated that dispersed TPD in a fluorine-containing polyimide matrix as a HTM has significantly improved device performance (Scheme 3.17) [91]. Flexible and fluorinated polyimide as a matrix exhibits the lowest turn-on voltage and a high EL efficiency [92]. 

Over the last decade, selected papers1114 have examined the deposition of fluoropolymers, using RF magnetron sputtering. All of these papers have examined the deposition of PTFE, with some of them2314 also studying the deposition of polyimide (PI) films. This chapter extends these studies and will report on the sputter deposition behavior of PTFE (polytetrafluoroethylene), PVDF (polyvinylidenefluoride), and FEP (fluorinated ethylene propylene copolymer) films. 

Fluorinated olefins, 77 866 Fluorinated organics, production of, 77 847 Fluorinated polyimides, 20 278 Fluorinated thermoplastics, 10 8 Fluorinated titanocycle, 25 118 Fluorinating agents, electrophilic, 77 847 Fluorination, 9 281, 678-679 aromatic ring, 77 866 chlorocarbons, 6 235 direct, 77 864, 882 electrochemical, 77 864—865, 882 of germanium, 72 552 halogen exchange, 77 861-864 selective, 77 831... 

In 1988 Heinze and Burton reported a facile synthesis of various a,p,P-trifluorostyrenes. These trifluorostyrene compounds were reported to be imstable to cyclodimerization at room temperature when stored neat, especially the compounds that were iara-substituted with electron-donating substituents. They described the preparation of one compound, l,4-bis(trifiuorovinyl)benzene with the observation that the material gelled when allowed to stand neat overnight. They offered the explanation that the gel was a polymer network connected with fluorinated cyclobutanes. Burton later went on to utilize this dimerization reaction for the cross-linking of polyimide thermoplastics. ... 

Pechar, T.W., Tspatsis, M., Marand, E., and Davis, R. (2002) Preparation and characterization of a glassy fluorinated polyimide zeolite mixed matrix membrane. Desalination, 146, 3-9. 

An alternative means of reducing the dielectric constant of polyimides is to have a low dielectric constant component dispersed as a second phase within the rigid polyimide matrix. Two key approaches have been pursued to this end. The first involves the preparation of polyimide block copolymers with highly fluorinated coblocks and the second involves the generation of a polyimide foam. The main drawback to the first approach is the solubility of highly fluorinated blocks in organic media which will permit copolymerization with polyimides. This led to the investigation of new semi-fluorinated polymers derived from polyfaryl ethers). 

The polyimide-perfluoroalkyl ether block copolymers were prepared through the poly(amic alkyl ester) route, where a solution of diester diacyl chloride of PMDA was added to a mixture of ODA and the perfluoroalkyl ether oH-gomer, analogous to the procedure previously described [55]. Toluene was used as a cosolvent together with NMP to improve the solubility of the fluorinated coblock, and the resulting polymers were isolated by precipitation. The charac-... 

F-BDAF Tg for various blend compositions, see Fig. 14. The microphase-separated morphology further manifests itself in the self-adhesion behavior of polyimide films derived from such mixtures. For mixture containing at least 25 wt% of the flexible component, peel tests of polyimide bilayer samples prepared by solution casting, bulk failure of the test specimens was observed. Since the flexible component contained fluorine, the samples could be examined by X-ray photoelectron spectroscopy to determine the surface composition. At only 10% loading, the flexible component comprised 100% of the top 75 A of the sample. The surface segregation of the flexible component is believed to be responsible for the adhesion improvements. 

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