Phenylated polyimides: Diels‐Alder reaction of biscyclopentadienones with dimaleimides

Abstract

A series of phenylated polydihydrophthalimides has been synthesized by the Diels‐Alder reactions of 3,3′‐(oxydi‐p‐phenylene)bis(2,4,5‐triphenylcyclopentadienone) and 3,3′‐(p‐phenylene)bis(2,4,5‐triphenylcyclopentadienone) with N,N′‐o‐, ‐m‐, and ‐p‐phenylenedimaleimide. The polydihydrophthalimides were soluble in dimethylformamide (DMF) and had intrinsic viscosities that ranged from 0.33 to 1.01, the polymers were dehydrogenated thermally and chemically to afford the corresponding phenylated polyphthalimides. The totally aromatic polyimides were also soluble in DMF but had intrinsic viscosities only as high as 0.41. The thermogravimetric analyses of the polyphthalimides showed breaks near 530°C in air and in nitrogen atmospheres.

Other synthetic routes to polyimides

“…Harris et al [80,81] The tricylic ketone moiety ofthe initial adduct spontaneously expelled carbon monoxide to form a dihydrophthalimide ring, which was readily oxidised with nitrobenzene to the final phthalimide group.…”

Polyimides

“…A second approach involves using maleimide-terminated monomers (bismaleimides or BMIs) in equal molar ratios with a dinucleophile, such as a diamine, or a diene like dibenzocyclobutane (BCB) and substituted dicyclopentadienes to form the corresponding linear polyaspartimides via Michael-type addition or the polyimides via a Diels-Alder [4 + 2] cycloaddition (Table 4) (104)(105)(106)(107)(108)(109)(110)(111)(112)(113)(114)(115). Linear polyimides can be synthesized directly from the A-B maleimidobenzocyclobutane monomers (116).…”

“…These reactions proceed without volatile evolution, but undergo thermally initiated retrograde reactions that lead to change in physical properties, chemical cross-linking, and aromatization of the cyclohexene ring (BCBs). Reactions involving BMIs with dicyclopentadieneones also proceed by a cycloaddition mechanism (114,115). This has the same advantage inherent to all Diels-Alder reactions in that no volatiles are generated.…”

“…However, with these pentadieneone dieneophiles, CO is eliminated forming a cyclohexadiene moiety. The cyclohexadiene can undergo further addition reactions or aromatize with the abstraction of two hydrogen atoms, depending on the reaction conditions and the added stability of any pendent substituents (114,115). This type of chemistry can be used to create photosensitive polyimides for imaging.…”

Synthesis and thermal properties of aryl‐substituted rod‐like polyimides

“…Different reaction systems are described in the literature. Very common are phenolic solvents (phenol, m-cresol, or p-chlorophenol) in combination with a catalyst or accelerator, such as isoquinoline, 5~13b,22 tertiary amines or p -hydroxybenzoic a~i d .~,~~,~~ Also polymerizations in nitrobenzene 25,26 or NMP 27 were investigated. Water formed during the imidization is removed by an inert gas stream or via an azeotrop.…”