ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 8, pp. 1476–1478. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © D.M. Mognonov, Zh.P. Mazurevskaya, V.V. Khakhinov, O.V. Il’ina, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81,
No. 8, pp. 1401–1403.
Manifestations of Crystallinity in Polyamidobenzimidazoles
D. M. Mognonov, Zh. P. Mazurevskaya, V. V. Khakhinov, and O. V. Il’ina
Baikal Institute of Nature Management, Siberian Branch, Russian Academy of Sciences,
Ulan-Ude, Buryatia, Russia
Received December 27, 2007
Abstract—Polyamidobenzimidazoles derived from 3,3',4,4'-tetraaminodiphenyl ether, diphenyl esters of
aliphatic and aromatic dicarboxylic acids, and ε-caprolactam were prepared by solid-phase polycondensation.
The relative degree of crystallinity, imparting the plasticity to the polymers as compared to the corresponding
polybenzimidazoles, was determined by X-ray phase analysis.
In this study, we examined the physicochemical-
properties of polyamidobenzimidazoles (PABIs) pre-
pared at various molar ratios of the starting monomers.
Polyamidobenzimidazoles were prepared by
solid-phase polycondensation from 3,3'4,4'-tetra-
aminodiphenyl ether (TADPE), diphenyl esters of
adipic (DPA), sebacic (DPS), isophthalic, and
terephthalic (DPT) acids, and ε-caprolactam (CL) .
The substances are copolymers of polybenzimidazole
(PBI) and polycaproamide (PCA), containing benzimi-
dazole rings and amide groups. The unit composition
depends on the starting monomers and their molar ratio
in the reaction mixture and, at equimolar ratio of
the comonomers, can be represented by the following
The polymers were purified by reprecipitation
from a solution in concentrated formic acid by dilution
with a small amount of water, avoiding turbidity, fol-
lowed by addition of a 0.5% solution of ammonium
carbonate. The product was filtered off on a Büchner
funnel, repeatedly washed with distilled water to neu-
tral reaction, and dried in a vacuum oven at 60–70°C.
The X-ray phase analysis was performed on a DRON-
UM1 diffractometer using Ni-filtered Cu
The thermal and chemical characteristics of PABIs are
given in , and some properties of the copolymers are
listed in the table.
The majority of PABIs are amorphous, but show
high resistance to acid and base agents and relatively
high strength preserved at elevated and low tempera-
tures . Such properties of the copolymers are due to
the presence of thermally stable benzimidazole rings,
and amide groups in PABI macromolecules make the
copolymers soluble in amide and other available or-
The relatively high structural regularity of the PA-
BIs containing aliphatic (sebacic acid) fragments can
be judged from the swellability in organic solvents
(dioxane, MEK). Experimental data show that this co-
polymer considerably swells (to up to 100%) and par-
tially dissolves upon heating. The Koenig hardness of
the polymer is 0.54, i.e., it has a high surface strength
and increased brittleness.
An increase in the length of aliphatic fragments in
the polymer (sebacic acid residues) leads to a rise in
its elasticity, as judged from the low hardness (0.045);
the polymer is in the hyper-elastic state. Swelling in
a solvent suggests its denser regular structure. After
heating, the polymer loses solubility.
In PABI, there are elements of crystallinity, par-
ticularly clearly manifested at the equimolar ratio of