Russian Journal of Applied Chemistry, 2011, Vol. 84, No. 9, pp. 1582−1586.
Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.I. Grachek, E.T. Krut’ko, L.Yu. Osmolovskaya, A.I. Globa, 2011, published in Zhurnal Prikladnoi Khimii, 2011, Vol. 84, No. 9,
AND POLYMERIC MATERIALS
Thermal Stabilization of Polyimides
with Boric Acid Esters
V. I. Grachek
, E. T. Krut’ko
, L. Yu. Osmolovskaya
, and A. I. Globa
Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Belarussian State University of Technology, Minsk, Belarus
Received December 30, 2010
Abstract—New and previously synthesized boric acid esters were tested as thermal stabilizing additives to
The resistance of polymeric materials to various
kinds of aging in the course of processing and service
determines the possible limits of their application.
Therefore, enhancement of the heat resistance of
polymeric materials and thus prolongation of their
reliable service life is an urgent problem of polymer
chemistry . Of much interest are multifunctional
stabilizers containing in one molecule several functional
groups acting by different mechanisms . Organoboron
compounds are among such stabilizers. Along with
enhancing the heat resistance, they act as fungicidal
additives to polymeric materials [3–5].
In this study we examined how boric acid esters
affect the heat resistance of polymeric materials. With
the aim to develop promising thermal stabilizers for
polyimides, we tested previously synthesized boric acid
esters and prepared new representatives of this class.
Н NMR spectra were recorded on a Tesla BS-
567 spectrometer (100 MHz) from solutions in СDСl
with HMDS as internal reference. The IR spectra were
measured with a Protégé 460 Fourier spectrometer
(Nicolet) from KBr pellets. The melting points of the
compounds were determined with a Koﬂ er bench.
Boric acid esters (BAEs) were prepared in one step
by heating boric acid with pyrocatechol and hydroxy
compounds at 70–80°С in benzene, with simultaneous
heteroazeotropic distillation of the water formed in
the reaction. The BAE structures were proved by IR
H NMR spectroscopy, mass spectrometry, and
The bands at 1350 ± 9 and 1040 ± 8 cm
IR spectra of BAEs characterize the symmetric and
asymmetric vibrations of В–О groups, and the bands
at 1240 ± 7 and 1090 ± 10 cm
, the symmetric and
asymmetric vibrations of С–О groups. The bands at
1410 ± 4 cm
belong to the vibrations of the С–N=О
group. The absorption band at 1642 cm
the vibrations of the СН=N azomethine group, and that
at 1607 ± 5 cm
, the vibrations of the С=N bond in
the ring. The band at 1757 cm
belongs to stretching
vibrations of the ester carbonyl group .
Н NMR and mass spectra of the compounds
synthesized are presented in Table 1.
As seen from Table 1, pyrocatechol ring protons give
signals at 6.21 ± 0.03 and 5.62 ± 0.02 ppm. The proton
of the azomethine group gives a signal at 8.16 ppm.
The mass spectra of BAEs contain medium-
intensity molecular peaks. The most characteristic and
the strongest peaks are those at m/z 135, 108, 92, and
65. Their origin can be associated with the C
fragment. As seen from Table 1, the intensity of
these peaks depends on the compound structure. The