2007_6_Nr6_EEMJ

Polyelectrolyte – surfactant complexes
At concentrations c > 10 -2 of the polymer
solution the formed complex precipitates entering in
the heterogeneous zone of complex formation. In the
analysed situations the concentrations for aggregation
and critical concentration of saturation have the same
values for every experiment, c ca = 4·10 -4 %, and c cs =
4·10 -3 %.
The results of the measurements of the
rheological study of complex solutions are presented
in Figs 5 – 8. Fig. 5 shows that the Praestol 611
solution has the Bingham pseudoplastic behaviour
0, 46
and the rheological model isτ
= 235,71+
138,44 & γ .
10 4
10 3
10 2
10 1
10 0
10 -1
Praestol 611 c = 0.1 and SLS c = 7.0 10 -4
complex solution
τ = f(γ)
η = f(γ)
10 5 γ, s -1
6x10 3
Solution of Praestol 611 c = 0,01%
10 -2
1 10 100 1000
5x10 3
a.
τ, N/m 2
4x10 3
3x10 3
2x10 3
1x10 3
going
return
Equation: y = a + b*x^c
a 235.71
b 138.44
c 0.46
0
0 200 400 600 800 1000 1200 1400
a.
γ, s -1
Praestol 611 c = 0.1 and SLS c = 1.2 10 -3
complex solution
10 5
10 4
10 3
10 2
10 1
10 0
10 -1
τ = f (γ)
η = f(γ)
Solution of Praestol 611 c = 0,01%
10 -2
10 100 1000
γ, s -1
100
b.
η, cP
10
going
return
1
1 10 100 1000
γ, s -1
Fig. 6. Rheograme of complex solution made with Praestol
611 c = 0.01% and SLS concentrations solutions c = 7 10 -4
% (a) and c = 1.2 10 -3 % (b)
The repetition of the experiment at the
increase and decrease of the share rate is presented in
Figs 8 – 9. The rheogrames show that under share
stress the structure of the polymer surfactant complex
restructures.
b.
Fig. 5. Rheograme of Praestol 611 c = 0.01 % solution at 20
°C in coordonate τ = f(γ) (a) and η = f(γ) (b)
The surfactant admixture in polymer solution
in low quantities (Fig. 6a) significantly modifies the
rheogram of the polymer solution (the value of
apparent viscosity lowers and for a certain value of
share rate it raises). The same effect but amplified can
be observed for admixture of greater quantities of
surfactant (Figs 6a, 7a and 7b).
4. Conclusions
The interaction between polyelectrolytes and
oppositely charged surfactants are experimentally
studied. At low concentrations, the surfactant binds
individually to the polyelectrolyte through
electrostatic interactions. A cooperative association
occurs at the critical aggregation concentration, c ac ,
when the surfactant aggregates are located along the
polyelectrolyte chain.
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