Chemistry Reference
In-Depth Information
Fig. 7 Second osmotic virial coefficient of sodium poly(styrene sulfonate) of varying molecular
mass (
M
) vs. the concentration of added NaCl:
squares
(23.4
10
5
);
diamonds
(22.8
10
5
);
triangles
(15.5
10
5
);
circles
(10
10
5
);
crosses
(3.9
10
5
);
plus
(3.2
10
5
) data from
Takahashi et al., 25
C[
57
];
half closed triangles
(12.2
10
5
);
stars
(7.3
10
5
);
inverted
triangles
(3.2
10
5
) data from Nordmeier, 20
C[
58
]
4 Gibbs Energy of Aqueous Solutions of Polyelectrolytes
For several reasons, it is rather difficult to develop a reliable method for describing
(i.e., correlating and predicting) the thermodynamic properties of aqueous solutions
of polyelectrolytes. The thermodynamics of polymer solutions in nonaqueous
systems as well as of aqueous electrolyte solutions are still major areas of research
and, consequently, the situation is less satisfactory for aqueous solutions of poly-
electrolytes, for which the dissociation reactions have to be taken into account. This
section reviews the most important features of some methods of modeling the Gibbs
energy of aqueous polyelectrolyte solutions. The Gibbs energy of an aqueous
solution is the sum of contributions from all (solute plus solvent) species
i
:
X
G
¼
n
i
m
i
;
(11)
i
where
n
i
and
m
i
are the number of moles and the chemical potential of component
i
(i.e., of the solvent and the solutes), respectively. It is common to split the Gibbs
energy into two parts, a contribution from ideal mixing and an excess contribution:
G
id
:
mix
:
þ
G
E
G
¼
:
(12)
