Synthetic aromatic polyimide scheme

The classical synthetic pathway to prepare polyimides consists of a two-step scheme in which the first step involves polymerization of a soluble and thus processable poly(amic acid) intermediate, followed by a second dehydration step of this prepolymer to yield the final polyimide. This preparative pathway is representative of most of the early aromatic polyimide work and remains the most practical and widely utilized method of polyimide preparation to date. As illustrated in Scheme 4, this approach is based on the reaction of a suitable diamine with a dianhydride in a polar, aprotic solvent such as dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dimethylformamide (DMF), or AT-methylpyrrolidone (NMP), generally at ambient temperature, to yield a poly(amic acid). The poly(amic acid) is then cyclized either thermally or chemically in a subsequent step to produce the desired polyimide. This second step will be discussed in more detail in the imidization characteristics section. More specifically, step 1 in the classical two-step synthesis of polyimides... 

To investigate the additional effect of triphe-nylamine (TPA) moieties on >C(CF3)2 containing polyimides, Liou et al. [183] synthesized a series of novel organo-soluble aromatic polyimides bearing pendant methoxy-substituted TPA moieties. They also prepared the same polyimide series without the >C(Cp3)2 group to compare their physical properties. A synthetic scheme of the TPA containing polyimide series is shown in Scheme 3.19. All of the... 

The synthesis of siloxane-polyimide elastoplastics requires an approach slightly different from that used in preparing the thermoplastic materials because of differences in reactivity between the aliphatic-anhydride-terminated siloxane oligomers and the aromatic dianhydrides. A one-pot condensation of the anhydride-terminated siloxane oligomers, BPADA, and the diamine in o-dichlorobenzene solution in the presence of 2-hydroxypyridine as catalyst leads to a siloxane-deficient polyimide. To circumvent this deficiency, a two-step synthetic scheme was used in which the anhydride-terminated siloxane oligomers were first capped with an excess of the diamine. The aromatic dianhydride was then added to the resulting amic acid oligomeric mixture and warmed to complete imidization (Scheme IV). 

Polyimides are class of polymers generally prepared from organic diamines and organic tet-racarboxylic acid dianhydrides by condensation polymerization. There are mainly two synthetic routes for polyimides one-step and two-step polymerization. Scheme 3.1 shows a generalized route of polyimide synthesis from an aromatic dianhydride and an aromatic diamine. 

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