Corona polyelectrolyte

Block copolymer micelles with a polyelectrolyte corona are a very important class of colloidal particles in aqueous medium and are often referred to as polyelectrolyte block copolymer micelles. The micellization behavior of these charged micelles has been very recently reviewed by Riess [14] and FOrster et al. [15]. A brief overview of the topic will therefore be presented in what follows. Amphiphilic block copolymers consisting of one hydrophobic block linked to one ionic block will only be discussed in this section. Blocks copolymers containing one hydrophilic block and one ionic block will be discussed in Sect. 4.3. 

For quite some time, there have been indications for a phase-separation in the shell of polyelectrolyte block copolymer micelles. Electrophoretic mobility measurements on PS-PMAc [50] indicated that a part of the shell exhibits a considerable higher ionic strength than the surrounding medium. This had been corroborated by fluorescence studies on PS-PMAc [51-53] and PS-P2VP-heteroarm star polymers [54]. According to the steady-state fluorescence and anisotropy decays of fluorophores attached to the ends of the PMAc-blocks, a certain fraction of the fluorophores (probably those on the blocks that were folded back to the core/shell interface) monitored a lower polarity of the environment. Their mobility was substantially restricted. It thus seemed as if the polyelectrolyte corona was phase separated into a dense interior part and a dilute outer part. Further experimental evidence for the existence of a dense interior corona domain has been found in an NMR/SANS-study on poly(methylmethacrylate-fr-acrylic acid) (PMMA-PAAc) micelles [55]. 

PB-core. The micellar core has a radius of Rc= 17 nm in good agreement with scattering experiments. It is surrounded by a thin dark layer which represents the dense interior part of the polyelectrolyte corona containing a high concentration of condensed counterions. 

Scaling Theory of Micelles with Polyelectrolyte Corona. 78... 

Crew-Cut Micelles with Quenched Polyelectrolyte Corona. 80... 

Crew-Cut Micelles with Annealing Polyelectrolyte Coronae. 94... 

Micelles with Quenched and Annealing Polyelectrolyte Coronae Nonlocal... 

Mean-Field Theory of Block Copolymer Micelles with Annealing Polyelectrolyte Corona... 

During the last decade, the potential for synthesis and constmction of novel complex multicomponent self-organized IPEC-based structures has considerably increased as polyelectrolytes and polyionic species with nonlinear topology have become available. Among those are polymeric nucelles with polyelectrolyte coronas, star-shaped polyelectrolytes, and cylindrical polyelectrolyte bmshes. Polyionic species of such types themselves possess often a pronounced capability for selforganization, which is expected to be enhanced when they are incorporated into complex macromolecular structures such as IPECs. The advanced IPECs based on polyionic species with nonlinear topologies are cmisidered in Sect. 3 of this review. 

Fig. 6 A polyelectrolyte star (a), a micelle with a polyelectrolyte corona (b), and a cylindrical polyelectrolyte brush (c)...

Ionic amphiphilic diblock copolymers are well known to self-assemble into core-corona aggregates (micelles) in aqueous media. The micelle comprises a hydrophobic core formed by nonpolar blocks and a hydrophilic corona built up from polyelectrolyte blocks. The properties of such macromolecular self-assemblies are reviewed in detail elsewhere [57, 58]. In many cases, the micelles are characterized by a spherical morphology. When the radius of the hydrophobic core is considerably smaller than the thickness of the polyelectrolyte corona, such macromolecular self-assemblies are regarded as star-like micelles (Eig. 6b). 

Amphiphilic block copolymers with one ionic block constitute an intriguing class of macromolecules, since their self-assembly in aqueous solution usually leads to the formation of spherical micelles with a hydrophobic core and a polyelectrolyte corona. These micelles are particularly interesting because the intrinsic properties of their polyelectrolyte corona are strongly influenced by many parameters like pH, salt concentration, degree of dissociation, polar interactions and so on. Moreover, they can be considered as a model to spherical polyelectrolyte brushes and thus provide a unique opportunity to study polyelectrolyte properties in high concentration conditions. The micellisation behaviour of ionic amphiphilic copolymers has been reviewed by Riess [1], Gohy [2], Eisenberg et al. [112, 113], Forster et al. [138] and Cohen Stuart et al. [139]. 

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