Polyimides alkyl-substituted

Bismaleimides undergo successive 2 + 2 and 2 + 4 cycloaddition reactions with benzene and alkyl-substituted benzenes on exposure to ultraviolet light. In the case of unsymmetrical bismaleimides or substituted benzenes, head-to-head, head-to-tail, and tail-to-tail polyimide structures are obtained. These polyimides are stable to >400°C. 

A unique photo-imagable polyimide, not intermediates but completely imidized form, was described by Pfeifer and Rhode [110], The polyimides were prepared from BTDA and diamines whose ortho positions to the amino groups were extensively substituted with alkyl groups. 

The selective stationary phases were further divided in the scheme proposed by Horning et al. [79] for the steroid separations into the types selective to alcohols, ketones, multiple bonds, etc. Here, various selective interactions between the column and the separated solutes are utilized. Most importantly, various polyglycols, polyesters, polyphenyl ethers, polyamides and polyimides belong to these categories. In addition, substitution of an alkyl group in a polysiloxane polymer by a more polar... 

Another recent example (Ford and Conner, 1994) is the alkylation of aniline or a substituted aniline with /j-isopropenylaniline (28) to give bisaniline A (29) with potential applications in polyamides, polyimides, and as a component in epoxy systems. 

Currently, it is known that high thermal and thermal-oxidative resistance in polyimide requires purely aromatic systems and that alkyl structures in the backbone or as substituents interfere with resistance. It is also assumed that further benzene rings in the backbone or hetero members between the benzene rings reduce resistance. Fluorine addition, on the other hand, improves resistance. Chlorine substitution results in improved resistance however, the results are ambiguous [572]. 

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