Direct polyimides

Quite recently we have found that the salt monomers were extremely reactive, producing directly polyimides in a very short reaction time (Eq. 5) [19]. In this connection, we have also found that the salt monomer method coupled with... 

A direct route to obtain polyimides and polybenzoxazoles without diacid has been explored by using direct carbonylation of an aromatic diiodo compound.100 The reactions were performed in polar aprotic solvent. The cheaper chlorine derivative can be used instead of the iodo one when it is located on a strongly... 

Direct food additives, 12 29, 34 categories of, 22 30 function of, 22 30 Direct formed polyimides, 20 284 Direct fuel cells, 22 221 Direct-gap semiconductors, 14 837 ... 

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... 

The most applied detectors are based on UV or fluorescence detection, both direct and indirect. For this purpose, a window has to be made on the polyimide coating of the fused silica capillary, simply by... 

Fig. 29. Preparation of insoluble cyclised polyimide (c) from soluble reactants (a) and soluble intermediate (b). LS is measured directly on solution (b), containing polymer of the same chain length as that of the polyimide118,119)...

The coating apparafus consisfs of a silk screen mesh fixed to a frame with sufficient tension to squeeze the ink through the screen and onto the blank substrate (e.g., polyimide). The substrate is fixed on an XY fable wifh adhesion fape, and fhe silken screen mesh is masked, wifh an open window in the center for screen printing. The silicon rubber squeeze is a fixed support and can be moved in both X and Y directions. A hot-air or IR ramp is used to dry the coating for solvenf removal. 

Direct copolymerization techniques have also been employed in the s)m-thesis of sulfonated poly(aryl ether ketones),i i polyimides, i 5 and poly(benzoimidazoles). The synthesis of random disulfonated biphenol poly(arylene ether sulfone) copolymers (BPSH x where x represents the percentage of disulfonated diphenylsulfone moieties in the polymer versus unsulfonated diphenylsulfone moities) (14) is shown in Scheme 3.5. 

With the work of Fenn and co-workers, liquid chromatography—electrospray interfaces for mass spectrometers were developed in 1984. Subsequently, the Pacific Northwest Laboratory began work in the area of CE—ESI—MS under the direction of Richard Smith and published the initial paper describing on-line CE—MS in 1987. Initial interface designs involved removing the polyimide at the end of the capillary in favor of a layer of silver for electrical contact. This interface was limited due to below optimum flow rates and limited lifetime of the metallized capillary. The introduction of the sheath flow design dramatically improved the CE—MS results. In lieu of being connected to a standard outlet buffer, the CE—MS interface used the outlet end of electrophoretic capillary connected directly to the electrospray mass spectrometer. 

Figure 23. Sulfonated diamines for direct synthesis of sulfonated polyimides.

Following this initial period of polyimide development, interest reached a steady-state and remained there until the late 1970s. During this time a major impetus to the polyimide area was provided by the aerospace industry. The need for composite matrix resins as well as structural adhesives with excellent oxidative and thermal stability appeared to be at least partially met by polyimide type resins. Ultimately, requirements of high flow and low void content in relatively thick parts directed these efforts into different directions. Another upswing occurred in the early 1980s with the potential application of... 

Initial investigations of base-catalyzed imidization of polymeric systems, in particular PMDA/ODA based polyfamic alkyl esters), have been difficult due to the insolubility of the polyimide precursor at imidization levels exceeding 40%. Nevertheless, preliminary studies indicate that the base-catalyzed polymer imidization reaction appears to be significantly slower at ambient temperatures as compared to the phthalamide model compounds. It is yet unclear whether this is a direct result of the conformational aspects associated with the polymer chain or solubility considerations arising from the less soluble, partially imidized polymer chain. Since much of the initial work involved IR studies of supported... 

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