It was found that the aggregation numbers of the original micelles hardly changes
upon their interaction with the oppositely charged linear polyions [61–64]. This
remarkable invariance of the aggregation numbers was observed not only for
“frozen” micelles such as PS-b-P4VPQ [63, 64] with a glassy PS block but also for
“dynamic” micelles such as the PIB-b-PMANa [61, 62] with a soft PIB block, which
can change their aggregation numbers with variations in environmental conditions [66].
This implies that the micelles act as peculiar macromolecular templates or
“nucleating” particles for a buildup of core–shell–corona architectures. At the
same time, it was shown that interpolyelectrolyte complexation does not render
the dynamic PIB-b-PMANa micelles frozen as their aggregation numbers remain
nevertheless sensitive to variations in the conditions of the surrounding solution
(e.g., pH) [62].
Finally, we should mention that IPECs based on micelles of ionic amphiphilic
diblock copolymers can participate in so-called polyion interchange (exchange
and substitution) reactions, accompanied by a transfer of GPE chains from one to
another HPE micelle. Such reactions were previously thoroughly investigated for
aqueous mixtures of oppositely charged linear polyelectrolytes [8, 31, 36, 67]. It
was found that the aggregation state of the polymeric component(s) involved in
such polyion interchange reactions has a remarkable effect on the reaction rate [68].
Specifically, the rate of the polyion interchange reaction decreased in the following
order: coil–coil (seconds) > coil–micelle (tens of seconds) > micelle–micelle
(thousands of seconds). A similar tendency was also observed for polyion coupling
(polyion addition) reactions, which result in the formation of IPECs, though in this
case the complexation between oppositely charged micelles (a micelle–micelle
system) was not examined [68].
3.3 IPECs Based on Cylindrical (Co)Polymer Brushes
Cylindrical polymer brushes (also referred to as molecular polymer brushes or
“bottle-brushes”) represent anisotropic macromolecules with cylindrical symmetry,
each containing a long linear backbone and a large number of rather short linear side
chains, which are densely attached to the backbone (Fig. 6c). Therefore, they have
a multitude of branching points located along the backbone. Cylindrical polymer
brushes can be synthesized via “grafting-from”, “grafting-to”, or “grafting-through”
approaches. Macromolecules of cylindrical polymer brushes exhibit a distinct wormlike morphology, which results from their pronounced anisotropic nature.
Recent advances in the synthesis of well-defined cylindrical ionic (co)polymer
brushes, which represent another type of branched ionic polymers [44], offer
the possibility of preparing their IPECs. An early attempt to obtain such macromolecular co-assemblies was made [69, 70] and describes formation of large
complex aggregates with a rod-like cylindrical morphology resulting from the
interaction of a PEO/PSSNa copolymer brush (so-called anionic prototype copolymer brush) with P4VPQ. These large rod-like co-assemblies are considered to
be highly anisotropic supermicelles.
Advanced Functional Structures Based on Interpolyelectrolyte Complexes
195
upon their interaction with the oppositely charged linear polyions [61–64]. This
remarkable invariance of the aggregation numbers was observed not only for
“frozen” micelles such as PS-b-P4VPQ [63, 64] with a glassy PS block but also for
“dynamic” micelles such as the PIB-b-PMANa [61, 62] with a soft PIB block, which
can change their aggregation numbers with variations in environmental conditions [66].
This implies that the micelles act as peculiar macromolecular templates or
“nucleating” particles for a buildup of core–shell–corona architectures. At the
same time, it was shown that interpolyelectrolyte complexation does not render
the dynamic PIB-b-PMANa micelles frozen as their aggregation numbers remain
nevertheless sensitive to variations in the conditions of the surrounding solution
(e.g., pH) [62].
Finally, we should mention that IPECs based on micelles of ionic amphiphilic
diblock copolymers can participate in so-called polyion interchange (exchange
and substitution) reactions, accompanied by a transfer of GPE chains from one to
another HPE micelle. Such reactions were previously thoroughly investigated for
aqueous mixtures of oppositely charged linear polyelectrolytes [8, 31, 36, 67]. It
was found that the aggregation state of the polymeric component(s) involved in
such polyion interchange reactions has a remarkable effect on the reaction rate [68].
Specifically, the rate of the polyion interchange reaction decreased in the following
order: coil–coil (seconds) > coil–micelle (tens of seconds) > micelle–micelle
(thousands of seconds). A similar tendency was also observed for polyion coupling
(polyion addition) reactions, which result in the formation of IPECs, though in this
case the complexation between oppositely charged micelles (a micelle–micelle
system) was not examined [68].
3.3 IPECs Based on Cylindrical (Co)Polymer Brushes
Cylindrical polymer brushes (also referred to as molecular polymer brushes or
“bottle-brushes”) represent anisotropic macromolecules with cylindrical symmetry,
each containing a long linear backbone and a large number of rather short linear side
chains, which are densely attached to the backbone (Fig. 6c). Therefore, they have
a multitude of branching points located along the backbone. Cylindrical polymer
brushes can be synthesized via “grafting-from”, “grafting-to”, or “grafting-through”
approaches. Macromolecules of cylindrical polymer brushes exhibit a distinct wormlike morphology, which results from their pronounced anisotropic nature.
Recent advances in the synthesis of well-defined cylindrical ionic (co)polymer
brushes, which represent another type of branched ionic polymers [44], offer
the possibility of preparing their IPECs. An early attempt to obtain such macromolecular co-assemblies was made [69, 70] and describes formation of large
complex aggregates with a rod-like cylindrical morphology resulting from the
interaction of a PEO/PSSNa copolymer brush (so-called anionic prototype copolymer brush) with P4VPQ. These large rod-like co-assemblies are considered to
be highly anisotropic supermicelles.
Advanced Functional Structures Based on Interpolyelectrolyte Complexes
195