1070-4272/01/7405-0839$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 5, 2001, pp. 839!844. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 5,
2001, pp. 814!819.
Original Russian Text Copyright + 2001 by Bogatyrev, Borisenko, Pokrovskii.
AND POLYMERIC MATERIALS
Thermal Degradation of Polyvinylpyrrolidone on the Surface
of Pyrogenic Silica
V. M. Bogatyrev, N. V. Borisenko, and V. A. Pokrovskii
Institute of Surface Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received November 20, 2000
Abstract-Thermal degradation of polyvinylpyrrolidone was studied by thermogravimetry, IR spectroscopy,
and thermal-desorption mass spectrometry.
Due to high complexing and adhesion properties,
nontoxicity, and solubility in water and most organic
solvents polyvinylpyrrolidone (PVP) is widely used in
various branches of industry . Along with common
use of PVP in medicine, pharmacology, and textile
industry, studies are actively pursued aimed at prepar-
ing new materials on its basis. Among them prepara-
tion of new copolymers and polymer blends including
organic-inorganic hybrid materials and nanocom-
posites is the most promising. Such polymer3silica
composites based on PVP were prepared by adsorp-
tion procedure [2, 3] or by grafting to the surface of
solid particles with formation of covalent bonds bet-
ween the polymer and SiO
[4, 5]. Previously, the
PVP3silica materials were used to prepare selective
membranes [6, 7], optical materials [8, 9], and chro-
matographic supports [10, 11].
In highly filled polymeric systems the fraction of
PVP units directly contacting with the silanol surface
groups of silica increases. It is known that the degree
of filling and the nature of the surface active groups of
dispersed filler significantly affect thermal and ther-
mal oxidative degradation of polymeric materials .
Since for PVP such data are lacking, the study of
thermal transformations of PVP in the adsorption
layers of various thickness on the surface of finely
dispersed silica is urgent.
In our work we used medical-grade PVP (Sintvita,
Russia) with an average molecular weight of 10700
and A-300 Aerosil pyrogenic silica (Khlorvinil,
Ukraine) with a specific surface area of 320 m
The samples were prepared as follows. First, a
dispersion of silica and a 10% solution of PVP in
distilled water were prepared, and the required amount
of the PVP solution was added to the silica dispersion.
Then the resulting mixture was thoroughly mixed and
after 1-h storage deposited on glass plates as thin
layers, which were dried at 80oC for 435 h. The prod-
uct was ground in an agate mortar and additionally
dried at 80oC for 1 h.
The silica samples with sorbed PVP were analyzed
for the carbon content on an AN-7529 express analyz-
er by combustion in an oxygen flow. The specific sur-
face area was determined by low-temperature desorp-
tion of argon according to the standard procedure.
The properties of the resulting PVP3silica samples are
listed in Table 1.
Thermal analysis was carried out using a Q-1500 D
derivatograph. The measurement parameters were as
follows: 500, 500, and 250 mV for TG, DTA, and
DTG, respectively; sensitivity 200 mg, and heating
rate 10 deg min
. The samples (300.16+0.24 mg)
were heated in a ceramic crucible.
The IR spectra were taken from pressed samples
). The thermal transformations were
studied using a heated quartz cell (CaF
Table 1. Properties of PVP3silica samples
³ PVP content ³
³ % ³ mmol g
1 ³ 3.8 ³ 5.8 ³ 0.52 ³ 258
2 ³ 8.2 ³ 12.6 ³ 1.14 ³ 217
3 ³ 11.0 ³ 16.9 ³ 1.52 ³ 183
4 ³ 15.8 ³ 24.3 ³ 2.19 ³ 128
5 ³ 19.0 ³ 29.3 ³ 2.64 ³ 65