Polyimides ethynyl

Ethynyl End-Capped Polyimide Oligomers Containing Oxyethylene Linkages... 

Oligomers of BTDA and Linear Diamines. A series of ethynyl end-capped polyimide oligomers was synthesized by the following route. 

The idea of synthesizing imide oligomers which carry acetylenic terminations appeared attractive because homopolymerization through acetylenic endgroups occurs without any volatile evolution and provides materials with good properties. Landis et. al (8,9) published the synthesis of such acetylene terminated imide oligomers from benzophenone tetracarboxylic anhydride, aromatic diamine and 3-ethynylaniline via the classical route. As usual, the amide acid is formed as an intermediate which, after chemical cyclodehydration, provides the polymide. Since ethynyl-terminated polyimide is used as a matrix resin for fiber composites, processing is possible via the amide acid, which is soluble in acetone, or via the fully imidized prepolymer, which is soluble in NMP. The chemical structure of the fully imidized ethynyl-terminated polyimide is provided in Fig. 44. 

In Table 1, the moisture uptake of cured and uncured Navy P3-2300-PE resin after 24 hours of immersion is compared to a number of other high-temperature polymer resins. The moisture uptake of the Navy P3 oligomer is nearly identical to that of the commercial P3 thermoplastic. Other commercial thermoplastics, such as poly(ether ether ketone), with very similar chemical compositions, exhibit similarly low levels of moisture uptake. On the other hand, the Navy P3 resins absorbs about 85% less water than the commercial polyimide Kapton HN. Since thermosetting phenyl ethynyl end-capped polyimides have moisture uptake characteristics that are similar to Kapton HN, with around 3% weight gain on exposure to 95% relative humidity (77), void-free composites based on Navy P3 resins should exhibit greatly reduced moisture uptake compared to those based on thermosetting polyimides. 

Fig. 17. TEM micrograph of crosslinked polyimide foam derived from imide/propylene oxide copolymer bearing ethynyl functionality...

Hanky and St. Clair evaluated [81] a series of imide oligomers end-capped with ethynyl groups. Polyamic acid 50 and polyimide 51 in Fig. 27 were prepared from BTDA 70, 3,3 -sulphonylbisbenzeneamine 49 and 3-ethynylbenzeneamine 45 with a degree of polycondensation n varying between 1 and 3. 

The cyclotrimerization of ethynylbenzene leads to 1,3,5-triphenylbenzene, and consequently polycyclotri-merization of bisethynylbenzene yields a high temperature stable polyphenylene resin.3° This chemical concept has been extended to develop the first ethynyl-terminated polyimide in the literature. " The following figure [7] outlines the synthetic route characterized by simply replacing some of the aromatic diamine with an ethynyl-substituted aromatic monoamine to provide a ethynyl-terminated polyimidf resin. 

From a practical viewpoint, the compounds most commonly used in the fabrication of addition polyimides are bismaleimides, bisnadimides and ethynyl terminated oligoimides [275]. Poly (bismaleimides) have actually achieved special importance as technical polymer materials [276]. Due to the aliphatic-type linkages, which appear as a consequence of polyaddition, polymers of this type are not as thermally stable as aromatic polyimides are. However, their good processability, the polymerization without volatiles release and the relative low cost of raw materials have helped them to become a real alternative for long term uses up to 200-250 °C. 

For the most demanding conditions poly(phenylquinoxaline) and polyimide oligomers were created, some end-capped only and others containing ethynyl pendant groups. Typical of the end-capped polyfphenylquinoxalines) are [597, 598] ... 

An ethynyl-containing system that reached commercialization is the one consisting of polyimide oligomers end-capped with ethynyl [597,598] and hindered ethynyl [600] reactive groups. Typical of the reactive oligomers marketed by Gulf Specialty Chemicals under the tradename Thermid is Ther-mid-M whose idealized structure is... 

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