Advances in Ma terials Physics and Che mist ry, 2012, 2, 177-180
doi:10.4236/ampc.2012.24B046 Published Online December 2012 (htt p://
Copyright © 2012 SciRes. AMPC
Investigation of the Surface Properties of Vinyl
Ethers – Sodi um 2-Acrylamido-2-Methylpropanesulfonate
S. Kh. Khussa i n, E. M. Shaikhutdinov, N . Zh. Seit kaliyeva, A. Zh. Zhenisova
Department of app l ied ch emis try, Kazakh National Technical University named after Kanysh Satpaev, Almaty, Kazakhstan
Received 2012
The surface properties of water soluble copolymers vinyl ethers of monoethanolamine and ethylene glycol with sodium
2-acryla mid o-2-methyl-propanesulfonate were investigated by studying adsorption at the aqueous solution air interface. It is found
that copolymers have considerably higher surface activity in comparison with poly- sodium
2-acryla mid o-2-methyl-propanesulfonate.
Keywords: Surface Active Copo lymers; Adsorption; Interface; Standard Free Energy of Adsorption
1. Introduction
Investigat io n of th e behavio r of macromolecu les at th e interface
is one of the biggest challenges because surface phenomena in
pol ymers and po lymeric material s play an i mportant role in the
whole complex of their properties, especially in their structural
and mechan ical propert ies.
The combination of the polar hydrophilic groups and non-
polar hydrophobic parts of chain in macromolecules gives to
the functional areas of polymers the surface-active properties
and the possibility to use them as flocculants, flotation reagents,
antistatic agents, stabilizers of disperse systems, etc., used in
the oil, pharmaceutical and textile industry, metallurgy, agri-
culture and for other purposes.
We have synthesized new multifunctional copolymers of
vinyl ethers of monoethanolamine and ethylene glycol with
sodium 2-acrylamido-2-methyl-propanesulfonate by free- radi-
cal copolymerization in aqueous medium [1,2].
This report is devoted to the determination of surface-active
properties of these copolymers by studying the adsorption at the
aqueous solution-air interface.
2. Experimental
The Na-AMPS monomer was prepared from 2-acrylamido-2-
methylpropanesulfonic acid (H-AMPS) (the content of the main
product was no less than 99 wt %) purchased from Avocado
Research Chemicals Ltd. (Switzerl and).
Ethylene glycol vinyl ether (EGVE) and monoethanolamine
vinyl ether (MEAVE) were purified by vacuum distillation
(Tb=72C/30 kP a, nD20= 1.4356 and Tb=4546C/1.333 kPa,
nD20= 1.4357 respectively).
The free-radical copolymerization of Na-AMS and MEAVE
was performed in an inert medium at 60°C at various molar
ratios of the starting monomers in aqueous solution. The reac-
tion was carried out in the presence of an equimolar mixture of
sodium bisulfite and potassium persulfate as a redox initiator.
The weight of the initiator was 0.1% with respect to the total
weight of comonomers.
The composition of the copolymer was determined by IR-
spectroscopy and potentiometric titration on an EV-74 ionome-
ter with t he use of glass and silver chloride elect r odes.
Adsorption of copolymers at the air-water solution interface
was studied by measuring surface tension. Surface tension (σ)
of polymer sodium 2-acrylamido-2-methyl-propanesulfonate
(Na-AMPS) aqueous solution, copolymer of ethylene glycol
vinyl ether- sodium 2-acrylamido-2-methyl- propanesulfonate
(EGVE-Na-AMPS), and copolymer of monoethanolamine
vinyl ether - sodium 2-acrylamido-2-methyl- propanesulfonate
(MEAVE-Na-AMPS) was measured at 298 K by the Wilhelmy
[3]. The σ value of solutions was calculated according to the
equati o n [4 ] :
2( )
m mg
where mp and ma - the mass of the plate in the solution and air,
respectively; ggravitational acceleration; l and d - the width
and thickness of the submerged part of the plate, respectively.
Retraction force of the plate to the solution was measured
usin g a t orsion balance to an accur acy of ±10-6 kg.
To determine the equilibrium value of surface tension, the
measure ment for each solu tion ther mostat icall y-controlled to an
accurac y of ± 0.5 0C was perfor med after 2 4 hou rs. The avera ge
value σ was found then from several measurements. The accu-
racy of surface tensio n measu rement did not exceed ±0 ,3 mN /
3. Results and Discussion
Figures 1 and 2 show kinetics of surface tension reduction of
the copolymer aqueous solution depending on adsorption time.
Copyright © 2012 SciRes. AMPC
It is evident that, for aqueous solutions of the copolymer, the
equilibrium value of surface tension (σ) is reached during sev-
eral hours, which is typical for high molecular surface active
The adsorption of macromolecules at interface has its own
peculiarities, among which the most important - the slowness of
the process [5]. It manifests itself, particularly, in reducing the
surface tension of aqueous solutions of macromolecular sub-
stances in the range of long t ime. The process can be divided in
two stages:
1) the diffusion of macromolecu les at th e interface
2) the restructuring of certain segments of the macromole-
cules o n polarity at the in terface und er the action of the su rface
force field.
In order to obtain information on the duration of the copoly-
mer adsorption the relaxation times of adsorbed layers were
calculat ed on kin etic dat e according t o equati on [6]:
lg (στ - σ) = lg (σ0 - σ) – τ / 2,3 ϑ, (2)
where στ - surface tension value of solution at time τ, mN/m;
σ0the initial of surface tension at τ = 0, mN/m; σthe
equilibrium value of surface tension (after 24 h.),mN/m; ϑ -
relaxation time of the adsorption layer, min.
m1 = 24.7 mol. MEAVE % in the polymer co mpos ition
Figure 1. Kinetics of the surface tension reduction of polymer
MEAVE - Na-AMPS at different concentrations of aqueous solu-
tions (wt %) in solution: 0.02 (1), 0.04 (2), 0.09 (3), 0.12 (4), 0.5 (5).
m1 = 30 mol.% VEEG in the polymer composition
Figure 2. Kinetics of the surface tension reduction of polymer
VEEG - Na-AMPS at differe nt concentrations of aqueous solutions
(wt %): 0.02 (1), 0.04 (2), 0.06 (3), 0.08 (4), 0.12 (5)
The relaxation times of polymer adsorption layers VEMEA -
Na-AMPS and VEEG-Na-AMPS at the interface solution - air
are shown in Table 1.
Analysis of the data (Table 1) shows that in the case of the
copolymer VEMEA-Na-AMPS relaxation time is directly pro-
portional to the concentration of the copolymer, whereas for the
copo lymer VEEG-Na-AMPS, this dependence passes through a
maximum. Obviously, this is due to the conformation of the
molecules of copolymers. At low concentrations of the solution
of the copol ymer macro molecules are i n a more expand ed con-
formation and reorientation of the branched structure of the
copolymer VEEG-Na-AMPS takes more time. Subsequent
increase of copolymer solution concentration raises quantity of
simultaneously adsorbing macromolecules which leads to de-
crease of vacant place on surface. As a result the reorientation
of macromolecular segments on polarity at the air- solution
interface becomes difficult and, hence, relaxation time of ad-
sorp tion layer decreas e [6] .
The isotherm of surface tension of copolymer solution VEEG
- Na-AMPS and MEAVE - Na-AMPS based on equilibrium
value of σ was constructed (Figure 3, curve 2,3), together with
Ta ble 1. The relaxation time of adsorption layers of copolymers MEAVE - Na-AMPS and VEEG - Na-AMPS at different concentrations of
Copolymer Concentration of copolymer, wt. % Relaxation time ϑ, min.
0,02 145
0,04 147
0,09 150
0,12 152
0,50 172
0,02 190
0,04 423
0,06 500
0,08 126
0,12 87
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Figure 3. Isotherms of surface tension of aqueous solutions poly-
NaAMPC (1) and copolymer MEAVE - Na-AMPS (3), copolymer
VEEG - Na-AMPS (2).
the isotherm of surface tension water solution poly- Na-AMPS
(Figure 3 , curve 1).
As can be seen from the Fig ure 3, the curve σ = f (c) of co-
polymer MEAVE - Na-AMPS is below the curve VEEG - Na-
AMPS, which indicates that surface activity of monoethanola-
mine vinyl ether copolymer is higher compared to VEEG -
Na-AMPS. The higher surface activity polymer VEMEA-Na-
AMPS explained by the formation of intramolecular salt bond
between a mino- and sulfonic acid groups, resulting in increased
hydrophobicity of the copolymer and is its compactness:
where R — (CH2)2 OH, and ( CH2)2 NH2
Based on isotherms the surface activity on Rebinder (GRe) for
poly- Na-AMPS and copolymers was determined according to
equat ion [7] (Table 2):
Re 0
= −
Table 2 demonstrates that surface activity of copolymer ex-
ceeds ones of homopolymer approximately more than 3 times.
Table 2. Physical - chemical properties of surface layers of polymers.
The system GRe10-3, (mN m-1) / (kmole m-3) ads G0298 , kJ / mole
Poly-Na-AMPS 1,5 1 8,0
Copolymer MEAVE - Na-AMPS 9,1 22,6
Copolymer VEEG - Na-AMPS 5,2 21,2
The values of polymer’s standard free energy of adsorption
(adsG0298) were calculated in order to identify the causes and
mechanism of change in surface activity and adsorption. In
addition, it is important characteristic of a spontaneous accu-
mulation of substance at the interface and is a measure of the
surface active macromolecu le’s desire to adsorb.
Standard free energy of adsorption was calculated according
to the equation [8]:
adsG0298 = -RT ln GRe, (4)
where T- the absolute temperature, R- the universal gas con-
As seen from the values shown in Table 2, the gain in stan-
dard free energy adsorption in transition from homopolymer to
copolymer VEEG- Na-AMPS is about 3 kJ/base-mole, and to
copolymer MEAVE - Na-AMPS is 4,6 kJ/base-mole.
Thus, the results of this study lead us to conclude that in
aqueous solutions the MEAVE - Na-AMPS and VEEG-Na-
AMPS copolymer have higher surface activity and adsorption
at the interface solution-air proceeds easier than poly-Na-
AMPS, i.e. vinyl ether u nits in the polymer chain increases the
surface activity of macr omolecules .
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Copyright © 2012 SciRes. AMPC
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