phase separation (precipitation) is observed in mixtures of the oppositely charged
polymeric components. It was found that the number of arms of the star-shaped HPE
determines a window of Z-values, which correspond to the formation of watersoluble nonstoichiometric IPECs, this effect becoming more pronounced with
increasing ionic strength of the surrounding solution [45].
A structural picture of complex species based on PANa stars was ascertained
for the star-shaped HPE having a large number of arms (21 arms) coupled with
a short linear polycation, quaternized poly(2-vinylpyridine) (P2VPQ), acting
as a GPE [46]. The authors suggested that each complex particle formed has
a compartmentalized structure of micellar (core–corona) type. A hydrophobic
complex core is composed of oppositely charged segments of the polymeric
counterparts while a hydrophilic corona, which grants to the whole macromolecular
co-assembly solubility in aqueous media, is built up from excess segments of HPE
(Fig. 7). If the total number of charged groups of the star-shaped HPE exceeds the
degree of polymerization of the linear GPE, then typically one polyelectrolyte star,
whose charge is partially compensated by chains of its polymeric counterpart, is
incorporated into each complex particle formed [45, 46].
An examination of such systems by means of molecular dynamic simulations
(Fig. 8) supported a proposed core–corona structure of nonstoichiometric IPECs
based on star-shaped polyions and further refined their structural picture [47]. It was
shown that some of the arms of the star-shaped HPE are completely chargecompensated by chains of the linear GPE and embedded into the core while the
remaining arms are free and build up an ionic corona (Fig. 8b). This pronounced
partition of arms between two populations explains an experimentally observed
hydrodynamic size invariance (or a slight change in a hydrodynamic size) of the
star-shaped HPE upon its loading with the oppositely charged linear GPE [45].
IPECs of very complex morphologies, such as long fibers forming fiber bundles or
double wall vesicles tending to aggregate, were observed upon the interaction of
oppositely charged cationic and anionic polyelectrolyte stars in extremely dilute
aqueous solutions, e.g., quaternized poly[2-(dimethylamino)ethyl methacrylate]
(PDMAEMAQ) stars and poly(methacrylic acid) (PMAA) stars, both having six
arms [48]. By adjusting the molecular weights of the star-shaped polyelectrolytes,
their concentrations, the matching degree of oppositely charged polymeric components, and preparation conditions, it is possible to tune different morphologies of the
resulting IPECs.
To broaden the window of Z-values corresponding to the formation of watersoluble IPECs, star-shaped polyions can be complexed with double hydrophilic
(bis-hydrophilic) diblock copolymers comprising an ionic block and a nonionic
hydrophilic block. In this case, the formed macromolecular co-assemblies remain
water-soluble even if oppositely charged groups of the polymeric counterparts are
taken in 1:1 ratio (Z ¼ 1) [49], provided that the length of hydrophilic nonionic
block is sufficiently long. Apart from the enhanced water-solubility of the formed
complex species, one can additionally impart new properties and desired
functionalities, such as biocompatibility, thermosensitivity, etc., through the hydrophilic nonionic block of the copolymer.
Advanced Functional Structures Based on Interpolyelectrolyte Complexes
189
polymeric components. It was found that the number of arms of the star-shaped HPE
determines a window of Z-values, which correspond to the formation of watersoluble nonstoichiometric IPECs, this effect becoming more pronounced with
increasing ionic strength of the surrounding solution [45].
A structural picture of complex species based on PANa stars was ascertained
for the star-shaped HPE having a large number of arms (21 arms) coupled with
a short linear polycation, quaternized poly(2-vinylpyridine) (P2VPQ), acting
as a GPE [46]. The authors suggested that each complex particle formed has
a compartmentalized structure of micellar (core–corona) type. A hydrophobic
complex core is composed of oppositely charged segments of the polymeric
counterparts while a hydrophilic corona, which grants to the whole macromolecular
co-assembly solubility in aqueous media, is built up from excess segments of HPE
(Fig. 7). If the total number of charged groups of the star-shaped HPE exceeds the
degree of polymerization of the linear GPE, then typically one polyelectrolyte star,
whose charge is partially compensated by chains of its polymeric counterpart, is
incorporated into each complex particle formed [45, 46].
An examination of such systems by means of molecular dynamic simulations
(Fig. 8) supported a proposed core–corona structure of nonstoichiometric IPECs
based on star-shaped polyions and further refined their structural picture [47]. It was
shown that some of the arms of the star-shaped HPE are completely chargecompensated by chains of the linear GPE and embedded into the core while the
remaining arms are free and build up an ionic corona (Fig. 8b). This pronounced
partition of arms between two populations explains an experimentally observed
hydrodynamic size invariance (or a slight change in a hydrodynamic size) of the
star-shaped HPE upon its loading with the oppositely charged linear GPE [45].
IPECs of very complex morphologies, such as long fibers forming fiber bundles or
double wall vesicles tending to aggregate, were observed upon the interaction of
oppositely charged cationic and anionic polyelectrolyte stars in extremely dilute
aqueous solutions, e.g., quaternized poly[2-(dimethylamino)ethyl methacrylate]
(PDMAEMAQ) stars and poly(methacrylic acid) (PMAA) stars, both having six
arms [48]. By adjusting the molecular weights of the star-shaped polyelectrolytes,
their concentrations, the matching degree of oppositely charged polymeric components, and preparation conditions, it is possible to tune different morphologies of the
resulting IPECs.
To broaden the window of Z-values corresponding to the formation of watersoluble IPECs, star-shaped polyions can be complexed with double hydrophilic
(bis-hydrophilic) diblock copolymers comprising an ionic block and a nonionic
hydrophilic block. In this case, the formed macromolecular co-assemblies remain
water-soluble even if oppositely charged groups of the polymeric counterparts are
taken in 1:1 ratio (Z ¼ 1) [49], provided that the length of hydrophilic nonionic
block is sufficiently long. Apart from the enhanced water-solubility of the formed
complex species, one can additionally impart new properties and desired
functionalities, such as biocompatibility, thermosensitivity, etc., through the hydrophilic nonionic block of the copolymer.
Advanced Functional Structures Based on Interpolyelectrolyte Complexes
189