Charge-transfer complexes polyimides

The fluorescence of polyimides yields information on the aggregation state of the polymer chains and on the formation of charge transfer complexes. Since the emission of the polyimide Kapton (29) is extremely weak, it had not been detected until the availability of highly... 

The emission intensity of blends of polyimides gives a measure of the degree of miscibility of two polymers.401 For example in blends of the strongly fluorescent polyimide (32) and the non-fluorescent polyimide (34) added at the level of 30 mo %, the intensity of the emission of (32) is quenched by half, indicating that the formation of intermolecular charge transfer complexes within (32) is disturbed significantly by the added polyimide. 

All of these approaches to making processable polyimides reduce several types of polymer interchain interactions, chain packing, and charge transfer electronic polarization interactions or charge transfer complex (CTC) formation. The current chapter presents a comprehensive review focusing on -C(CF3)2-and -CF3-based aromatic polyimides that have been developed between 2000 and 2010, such as low dielectric constant polymers, and well as membrane-based applications such as pervaporation, fuel cell, and gas separation. 

Electrooptic bistability of a Ferroelectric Liquid Crystal Device prepared using charge transfer complex doped polyimide orientation films. Figures 1 and 2, K. Nakaya, B.Y. Zhang, M. Yoshida, I. Isa, S. Shindoh and S. Kobayashi, Japanese Journal of Applied Physics, 28 (1), p. L116 (1989). Reproduced by permission of Institute of Pure and Applied Physics. 

Enhancement of bistability by doping polyimide alignment layers with a charge transfer complex (CTC) and an appropriate rubbing process has been reported [34]. 

In order make an effort to bring the polyimide-metal adhesion problem to an even more fundamental level, we have previously proposed that model molecules, chosen as representative of selected parts of the polyimide repeat unit, may be used to predict the chemical and electronic structure of interfaces between polyimides and metals (12). Relatively small model molecules can be vapor deposited in situ under UHV conditions to form monolayer films upon atomically clean metal substrates, and detailed information about chemical bonding, charge transfer and molecular orientation can be determined, and even site-specific interactions may be recognized. The result of such studies can also be expected to be relevant in comparison with the results of studies of metal-polymer interfaces. Another very important advantage with this model molecule approach is the possibility to apply a more reliable theoretical analysis to the data, which is very difficult when studying complex polymers such as polyimide. 

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