Chemistry Reference
In-Depth Information
Fig. 5 Reduced osmotic pressure vs. polymer concentration for NaPSS at 25
C in aqueous NaCl
solutions of various ionic strength
I
:
open squares
I = 0.005 mol/dm
3
;
open circles
I = 0.01 mol/
dm
3
;
open triangles
I = 0.02 mol/dm
3
;
open diamonds
I = 0.05 mol/dm
3
;
open inverted triangles
I = 0.1 mol/dm
3
;
crosses
0.5 mol/dm
3
[
26
]
sulfonic acid groups at constant ionic strength [fixed by a mixture of NaNO
3
þ
Pb
(NO
3
)
2
], the relative amount of sulfonic acid groups neutralized by lead ions (
y
Pb
)
also increases and, consequently, the relative amount of sulfonic acid groups
neutralized by sodium ions (
y
Na
) decreases. However, the decrease of
y
Na
is not
completely compensated by the increase of
y
Pb
and, therefore, the relative amount
of dissociated sulfonic groups increases.
y
Pb
decreases and
y
Na
increases when the
ionic strength is increased at constant lead concentration. The sum (
y
Pb
þ y
Na
) also
increases because at the higher ionic strength more ionic species compete for the
charged repeating units of the backbone. When, at constant ionic strength, sodium
nitrate is replaced by nitric acid,
y
Pb
increases and
y
Na
decreases and the sum
(y
Pb
þ
y
Na
) reveals a small change.
There are also many reports on the application of low angle static light scatter-
ing, particularly laser light scattering, in investigations of aqueous polyelectrolyte
solutions. Light scattering experiments are common for determining the mass-
averaged molecular mass of a polymer, but the technique has also been applied to
the determination of osmotic virial coefficients in aqueous solutions.
Osmotic virial coefficients are commonly used to express the osmotic pressure
p
as a function of solute concentrations. For an aqueous solution of a single solute the
osmotic virial equation is:
RT
¼
~
c
s
M
n
þ ~
c
s
A
s;s
þ ~
c
s
A
s;s;s
þ :::;
(10)
