1070-4272/01/7407-1203$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 7, 2001, pp. 1203!1206. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 7,
2001, pp. 1170!1173.
Original Russian Text Copyright + 2001 by Igrunova, Sirotinkin, Uspenskaya.
AND POLYMERIC MATERIALS
Behavior of Tetrazole-containing Acrylic Hydrogels
in Electrolyte Solutions
A. V. Igrunova, N. V. Sirotinkin, and M. V. Uspenskaya
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received March 16, 2001
Abstract-The influence of temperature, pH, and chemical composition of the medium on the equilibrium
swelling of polymeric polyelectrolytic tetrazole-containing acrylic hydrogels was examined.
Interaction of hydrogels with electrolyte solutions,
resulting in limited swelling, is actively studied for a
long time. Polyelectrolytic hydrogels are of interest
from the viewpoint of both modeling of bioinforma-
tion systems and various practical applications: agri-
cultural gels, gels for sanitation purposes used for
water treatment, etc. Wide prospects are opened by
the possibility of varying the phase state of polymeric
gels, i.e., of performing transitions between the
swollen and collapsed states, under the action of
minor changes in the medium. In the past decade
major attention has been given to hydrogel systems
sensitive to fluctuations of temperature, pH, and ionic
strength of solution [1, 2].
Complexation of polymers with metal ions can
both increase and decrease the degree of swelling .
Modification of the chemical structure of acrylic
hydrogel with various comonomers can also affect the
degree of swelling in salt solutions.
In this work we studied the features of behavior of
polymeric hydrogels of acrylic acid (AA), 2-methyl-
5-vinyltetrazole (MVT), and methylenebisacrylamide
in various electrolyte solutions and the influence of
temperature on the water absorption of the polymers.
Hydrogels based on AA and MVT or methylene-
bisacrylamide (MBAA) as a cross-linking agent were
prepared by polymerization in aqueous solution at
60oC in the presence of the initiating system am-
monium persulfate (AP)3tetramethylethylenediamine
(TMED). The content of the components was as fol-
lows (wt %): monomers 30, cross-linking agent 0.13
0.9, and MVT 15370. The features of synthesis and
gelation are described elsewhere .
The degree of equilibrium swelling was measured
by the standard gravimetric procedure and calculated
by the equation
is the weight of the swollen sample and m
is that of the dried sample (g).
In calculations, we averaged the results for five
similar samples. The solution pH was monitored with
a pH-150 digital pH meter.
The influence of the swelling3drying cycles on the
absorption capacity of the hydrogels was studied as
follows. Samples of dry hydrogels were placed in an
excess of distilled water and kept at 50oC to attain the
equilibrium swelling. After separation from the non-
absorbed water, the gel was dried at 50oC to constant
weight. The cycles were repeated until the gel either
dissolved or lost the absorbing power because of
The behavior of acrylic hydrogels modified with
MVT in electrolyte solutions has certain specific
features. The major advantage of new hydrogels is the
high degree of equilibrium swelling in <10
tions of polyvalent metal salts. Under these condi-
tions, the degree of equilibrium swelling of hydrogels
in solutions of cobalt, nickel, and copper salts was
more than 200 g g
. In some cases at a low salt con-
M) the degree of equilibrium
swelling of the gel was higher than in distilled water
. Figure 1 shows how the degree of equilibrium
swelling of the gel containing 43.5 wt % MVT and
0.1 wt % MBAA (in the monomeric mixture) depends
on the concentrations of NaCl and CoCl
and on the
solution pH. The degree of swelling of tetrazole-