ИСТИНА

The interaction of micelles generated in aqueous solutions of polyisobutylene-block-poly(methacrylic acid) diblock copolymers (PIB(X)-b-PMAA(Y); X and Y are DPns of the corresponding blocks: X = 20, Y = 100, 280, 425; X = 30, Y = 190; X = 75, Y = 190, 615, 1590) with the strong linear cationic polyelectrolyte, poly-N-ethyl-4-vinylpyridinium bromide P4VP*EtBr (DPw = 480, 3000), was demonstrated (by means of a combination of turbidimetry, analytical ultracentrifugation, light scattering, fluorescence spectroscopy with the use of pyrene as a probe, and small-angle neutron scattering) to result in the formation of novel water-soluble micellar interpolyelectrolyte complexes (IPECs) in which the original copolymer micelles play a lyophilizing part (pH > 6.5, [NaCl] < 0.3 M). Such IPECs are considered to have a "core-shell-corona" ("onion"-like) architecture: each complex particle consists of a hydrophobic core built up from the PIB blocks, which is surrounded by a shell assembled from the interacting oppositely charged polyelectrolyte fragments, and an ionic corona built up from the excess fragments of the PMAA blocks not involved in the interpolyelectrolyte complexation. The formation of the complex micelles is assumed to result from a peculiar assembly process including binding of the cationic macromolecules to periphery parts of the PIB(X)-b-PMAA(Y) micelles, followed by their penetration deeply inside of the micellar coronae via polyion exchange reactions and final localization in vicinities of the micellar cores. A response of the micellar IPECs to the variations of pH and ionic strength of the surrounding solution was examined and compared with the behavior of the reference water-soluble IPECs resulting from the interaction between the corresponding linear homopolyelectrolytes, PMAA (DPw = 3000) and P4VP*EtBr. As the reference complexes, the complex micelles were shown to loose their solubility at pH < 6.5 due to protonation of carboxylate groups. In contrast to the reference complexes, no salt-induced phase separation in solutions of the micellar IPECs (pH > 6.5) was observed. The electrostatic interaction between the PIB(X)-b-PMAA(Y) micelles and P4VP*EtBr was found to be suppressed at rather high ionic strength of the surrounding medium ([NaCl] > 0.3 M) due to the screening effect of small ions. The salt-induced dissociation of the water-soluble micellar IPECs was shown to take place only when the certain critical concentration of NaCl [NaCl)d is reached, proceeding at [NaCl] > [NaCl]d via a gradual release of the cationic macromolecules from the complex particles upon increasing ionic strength of the surrounding medium.