Amorphous polyacrylonitrile: Synthesis and characterization

Abstract

SynopsisAmorphous polyacrylonitrile was successfully synthesized with bis(pentamethy1eneimino)magnesium in heptane at 70°C. The amorphousness of the polymer increased with rising polymerization temperature and was favored by the nonpolar solvent. The polymer showed regular head-to-tail sequences which were confirmed by converting the polymer into polyacrylic acid and polymethylacrylate. The amorphous PAN produced a broad x-ray diagram with a maximum at 20 = 16.1' and a less intense halo a t 20 = 27.5'. This pattern did not change after heat treatment. The synthesis of amorphous PAN strongly supports Imai's hypothesis that polyacrylonitrile consists of paracrystalline and amorphous phases. The amorphous PAN also tends to support Minami's assignment of the two absorptions in the temperature dependence of the dynamic loss tangent; the absorption a t the lower temperature (110OC) is due to molecular motions in the paracrystalline phase and the absorption a t the higher temperature (160°C) is attributed to the molecular motions in the amorphous region.

Dynamic mechanical thermal and infrared analyses of polyacrylonitrile ?electrografted? onto a metal

“…plexes in host materials, such as urea canals and b-cyclodextrin, 25 and anionic polymerization initiThe question might address why neither Joh 14 nor Minami et al 11 observed the T 0 transition in ated by metal derivatives bearing sterically crowded ligands.…”

“…The assignment of the amorphous transition It is noteworthy that no mechanical testing has was also supported by Joh,14 who studied a highly been reported until now in order to probe the main amorphous PAN synthesized in heptane at 70ЊC relaxations characteristic of the ''grafted'' PAN with bis(pentamethyleneimino) magnesium as a chains, which might provide valuable information polymerization catalyst. According to this author, on chain structure.…”

“…the film thickness is increased. The assumption by Joh that the amorphous Finally, the effect of the deposition potential on structure of PAN would depend on the chain isothe dynamic mechanical properties of the tacticity 14 appears to be a reasonable explanation ''grafted'' films has also been emphasized. The for the observed shift in T 1 .…”

Polyacrylonitrile-based nanocomposite fibers: A review of current developments

“…Nitrile polymerization may lead to forming a ladder structure. 13 PAN yields up to 65% carbon upon carbonization. PAN was first developed for fiber manufacturing in 1940 by DuPont.…”

Dynamic Mechanical Relaxations in Poly(acrylonitrile) with Different Stereoregularities

“…14,26 Another reason that ambiguities still remain is related to the fact that at-PAN shows no melting in bulk, 27 and it was difficult to prepare wide varieties of morphologies that might allow the correlation of each of the properties to its specific morphological origin. Furthermore, the fact that some of the fibers previously used were copolymers of acrylonitrile containing a small percentage of comonomers 13,18,22 or had heterotactic linkages such as chain branching 19 might also lead to the confusion.…”