Crystal structure of poly(m‐phenylene isophthalamide)

Abstract

The crystal structure of poly(m‐phenyulene isophthalamide) was determined by x‐ray analysis. The triclinic cell, with a = 5.27 Å, b = 5.25 Å, c (fiber axis) = 11.3 Å, α = 111.5°, β = 111.4° and γ = 88.0° and space group P1, contains one monomeric unit. The crystal density is 1.47 g/cc. The molecules in the crystal are contracted by 1 Å per monomeric unit from the fully extended conformation, and the planes of the benzene rings and adjacent amide groups make angles of about 30°. The crystal is composed of molecular chains connected by NH···O hydrogen bonds along the a and b axes forming a “jungle gym” network structure. The low tensile modulus of this polymer as compared with that of poly(p‐phenylene terephthalamide) is attributed to the contracted molecular conformation.

Strain-dependent dynamic mechanical properties of Kevlar to failure: Structural correlations and comparisons to other polymers

“…Its amine functional group is situated with the meta orientation on the phenyl ring in a monomer unit, as opposed to the para configuration in Kevlar. This small difference in molecular structure changes the optimal bond angles of phenyl-nitrogen and phenyl-carbon bonds in Nomex, resulting in a "crumpled" chain structure that cannot crystallize into stacked sheets [7]. This causes it to take on a "jungle gym" structure [7], with randomly stacked polymer chains, and a resulting lower overall crystallinity than Kevlar [7].…”

“…In this regime, as above, chains begin to unravel, increasing structural disorder. Regime II begins after the loss factor reaches a maximum, and the "jungle gym" [7] structure in Nomex begins to align with the tensile axis. As above, a very slight leveling-off of the loss factor decrease is observed with increasing strain in this regime, due to molecular-level chain alignment reaching a maximum.…”

Hollow spheres of aromatic polyamide prepared by reaction‐induced phase separation

“…It has been reported that highly crystalline poly(1,4-phenylene isophthalate) were obtained as precipitated plate-like crystals by the reaction-induced crystallization during the polymerization of isophthalic acid and PPDA. 22 The PPHIA hollow spheres were formed via the liquid-liquid phase separation. The PPHIA hollow spheres possessed high crystallinity, nevertheless the liquid-liquid phase separation mode, bulky OH substituent and the irregular cross-linking structure ought to lower the crystallinity.…”

Preparation of graphene oxide modified poly(m-phenylene isophthalamide) nanofiltration membrane with improved water flux and antifouling property

“…In a word, membranes which were prepared by first blending GO in the polymer dopes and then undergoing phase inversion protocol exhibited higher water flux and improved antifouling properties. Poly (m-phenylene isophthalamide) (PMIA) has great thermal resistivity (T g 270 • C), good chemical stability, elongation at break and toughness as well as high mechanical strength, which explains PMIA is an outstanding membrane material [38][39][40]. Wang et al fabricated a PMIA hollow fiber NF membrane that could effectively remove a persistent organic pollutant, perfluorooctane sulfonate (PFOS), from water [41].…”