Polyion coacervate micelles

When the coordination polymer is mixed with an oppositely charged neutral diblock polymer, the electrostatic interaction will drive complex coacervate formation [40]. But, the growth of the complex coacervate will be constrained by the presence of the neutral blocks, and be stabilized at a finite size. In this way, so-called complex coacervate core micelles (C3Ms), or polyion coacervate (PIC) micelles are formed. This micelle formation is analogous to the formation of C3Ms in covalent polyelectrolyte/ block polymer systems [67, 68]. Obviously, the coordination polymer,... 

These particles are called by several names in literature block ionomer complexes [57], polyion complex micelles [58], complex coacervate core micelles [59] and polyelectrolyte complex micelles. An extensive review of this type of micelle has been written by Voets et al. [60]. 

Another interesting system is based on the adsorption of so-called complex coacervate core micelles (also called polyion complex micelles) [28,29]. These micelles are formed in aqueous solution when two oppositely charged polyelectrolytes are mixed, with at least one of these polyelectrolytes being connected to an uncharged and water-soluble polymer. The complexed polyelectrolytes then form the complex coacervate core of the micelles, while the neutral chain forms the corona. These micelles have been shown to adsorb to surfaces with very different properties, such as silica and polystyrene. Although formed brushes are of low density, good antifouling properties have been observed [28,30]. 

Water-soluble interpolyelectrolyte complexes (IPECs) can be prepared by complexation of amphiphihc block copolymers, which comprise a hydrophobic block and an ionic or hydrophilic nonionic block [81,82]. Double hydrophilic block copolymers having an ionic block and a nonionic one can be prepared for IPECs even in 1 1 charge-to-charge ratio of the polymeric components in aqueous solution [81]. IPECs normally have a core/corona structure and are often referred to as polyion complex micelles, complex coacervate micelles, or block ionomer complexes [83,84]. 

The results of experimental and theoretical research on water-soluble (nonstoichio-metric) IPECs based on nonlinear (branched) polyionic species (HPE) complexed with oppositely charged linear PEs (GPE) demonstrated that the main feature of such macromolecular co-assemblies is their pronounced compartmentalized structure, which results from a distinctly nonuniform distribution of the linear GPE chains within the intramolecular volume of the branched HPE. In the case of star-shaped PEs or star-like micelles of ionic amphiphilic block copolymers, this com-partmentalization leads to the formation of water-soluble IPECs with core-corona (complex coacervate core) or core-shell-corona (complex coacervate shell) structures, respectively. Water-soluble IPECs based on cylindrical PE brushes appear to exhibit longitudinally undulating structures (necklace) of complex coacervate pearls decorated by the cylindrical PE corona. 

Polyanions and polycations can co-react in aqueous solution to form polyelectrolyte complexes via a process closely linked to self-assembly processes [47]. Despite progresses in the field of (inter-) polyelectrolyte complexes [47] (IPEC from Gohy et al. [48], block ionomer complexes BIC from Kabanov et al. [49], polyion complex PIC from Kataoka and colleagues [50, 51], and complex coacervate core micelles C3M from Cohen Stuart and colleagues [52], understanding of more complex structures such as polyplexes (polyelectrolyte complexes of DNA and polycations) [53] is rather limited [54]. It has also to be considered that the behavior of cationic polymers in the presence of DNA and their complexes can be unpredictable, particularly in physiological environments due to the presence of other polyelectrolytes (i.e., proteins and enzymes) and variations in pH, etc. 

In a different context, complex coacervate core micelle can be obtained by the reaction of a polyion-neutral diblock copolymer with an oppositely charged polyelectrolyte. These micelle are formed upon hierarchical self-assembly in water of the two polymeric components and, more interestingly, upon self-assembly of metal ion coordination polymers [47],... 

Keywords Polyelectrolyte Co-assembly Responsive Complex coacervate Polyion Micelle... 

---