reaction also strongly increases with the decreasing linear charge density of GPE as
well as with the decreasing degree of polymerization of the latter [36].
The considered processes play an extremely important role during preparation of
IPECs. Thus, mixing aqueous solutions of oppositely charged polyelectrolytes at
charge-to-charge ratios at which water-soluble nonstoichiometric IPECs are to be
finally formed results, at first, in appearance of turbidity in the system. However,
the turbidity gradually disappears with time, depending on the mixing conditions,
and particles of a nonstoichiometric IPEC with ’ ¼ Z can be detected in the system
[36]. The first, rapid stage of the reaction proceeds with a diffusion-controlled rate.
It is accompanied by appearance of rather large aggregates, whose charge-to-charge
stoichiometry differs from the charge-to-charge stoichiometry of the reaction
mixture, i.e., ’ 6 ¼ Z. The next, relatively slow stage is a polyion exchange between
these aggregates and free HPE, leading to the formation of thermodynamically
stable water-soluble nonstoichiometric IPECs.
The processes described above are also of importance for insoluble stoichiometric
IPECs as well as for IPEC-based materials, including composites. This manifests
itself in the fact that the swollen-in-water IPECs behave as viscous liquids and can
creep. When incorporated into complex disperse systems (e.g., soils), they quickly
recognize complementary sites on the surface of soil particles and strongly stick them
together. In such systems, oppositely charged polyions constantly migrate relative to
each other due to Brownian motion, remaining at the same time incorporated into the
IPECs [8]. This behavior explains the fact that composites based on such macromolecular co-assemblies in a wet state exhibit pronounced self-healing behavior.
The results of studies on the kinetics of interpolyelectrolyte exchange reactions
provide evidence that fluorescent labels of HPE*, which were taken to be hydrophobic, act as “anchors” for GPE-quenchers. It was found that an antracenyl label
is a weak “anchor” compared to a pyrenyl label and that an increasing amount of
labels in a HPE* chain leads to its more selective binding with GPE-quenchers [36,
37]. This is because of an additional gain of free energy upon formation of a contact
between a label and a monomer unit of the polymeric quencher due to the
donor–acceptor interaction and also because of incorporation of the label into a
rather hydrophobic domain consisting of hydrophobic moieties of the coupled
polyions. Such “recognition” plays an important role in biological systems.
Analysis of the equilibrium of interpolyelectrolyte coupling and kinetics of
interpolyelectrolyte exchange led to the conclusion that IPECs are stable macromolecular co-assemblies. In aqueous media, IPECs do not dissociate to their polymeric
components at concentrations of low molecular weight salts typically below about
0.5 M and, at the same time, retain high dynamics. At such salt concentrations,
polyions building up macromolecular co-assemblies at ambient temperatures are able
to easily migrate with respect to each other. In aqueous solutions of nonstoichiometric
IPECs, GPE chains easily change their hosts through interpolyelectrolyte exchange
reactions. These processes provide remarkable self-organization of IPECs. Being of a
pronounced amphiphilic character, IPECs quickly find their optimal location in a
complex environment. Thus, they “recognize” complementary sites on surfaces of
particles in natural dispersions and anchor onto them, as depicted in Fig. 5.
184
D.V. Pergushov et al.
well as with the decreasing degree of polymerization of the latter [36].
The considered processes play an extremely important role during preparation of
IPECs. Thus, mixing aqueous solutions of oppositely charged polyelectrolytes at
charge-to-charge ratios at which water-soluble nonstoichiometric IPECs are to be
finally formed results, at first, in appearance of turbidity in the system. However,
the turbidity gradually disappears with time, depending on the mixing conditions,
and particles of a nonstoichiometric IPEC with ’ ¼ Z can be detected in the system
[36]. The first, rapid stage of the reaction proceeds with a diffusion-controlled rate.
It is accompanied by appearance of rather large aggregates, whose charge-to-charge
stoichiometry differs from the charge-to-charge stoichiometry of the reaction
mixture, i.e., ’ 6 ¼ Z. The next, relatively slow stage is a polyion exchange between
these aggregates and free HPE, leading to the formation of thermodynamically
stable water-soluble nonstoichiometric IPECs.
The processes described above are also of importance for insoluble stoichiometric
IPECs as well as for IPEC-based materials, including composites. This manifests
itself in the fact that the swollen-in-water IPECs behave as viscous liquids and can
creep. When incorporated into complex disperse systems (e.g., soils), they quickly
recognize complementary sites on the surface of soil particles and strongly stick them
together. In such systems, oppositely charged polyions constantly migrate relative to
each other due to Brownian motion, remaining at the same time incorporated into the
IPECs [8]. This behavior explains the fact that composites based on such macromolecular co-assemblies in a wet state exhibit pronounced self-healing behavior.
The results of studies on the kinetics of interpolyelectrolyte exchange reactions
provide evidence that fluorescent labels of HPE*, which were taken to be hydrophobic, act as “anchors” for GPE-quenchers. It was found that an antracenyl label
is a weak “anchor” compared to a pyrenyl label and that an increasing amount of
labels in a HPE* chain leads to its more selective binding with GPE-quenchers [36,
37]. This is because of an additional gain of free energy upon formation of a contact
between a label and a monomer unit of the polymeric quencher due to the
donor–acceptor interaction and also because of incorporation of the label into a
rather hydrophobic domain consisting of hydrophobic moieties of the coupled
polyions. Such “recognition” plays an important role in biological systems.
Analysis of the equilibrium of interpolyelectrolyte coupling and kinetics of
interpolyelectrolyte exchange led to the conclusion that IPECs are stable macromolecular co-assemblies. In aqueous media, IPECs do not dissociate to their polymeric
components at concentrations of low molecular weight salts typically below about
0.5 M and, at the same time, retain high dynamics. At such salt concentrations,
polyions building up macromolecular co-assemblies at ambient temperatures are able
to easily migrate with respect to each other. In aqueous solutions of nonstoichiometric
IPECs, GPE chains easily change their hosts through interpolyelectrolyte exchange
reactions. These processes provide remarkable self-organization of IPECs. Being of a
pronounced amphiphilic character, IPECs quickly find their optimal location in a
complex environment. Thus, they “recognize” complementary sites on surfaces of
particles in natural dispersions and anchor onto them, as depicted in Fig. 5.
184
D.V. Pergushov et al.